Publications by authors named "Shengqian Ma"

176 Publications

Indium-Organic Framework with Topology as a Versatile Catalyst for Highly Efficient One-Pot Strecker Synthesis of α-aminonitriles.

ACS Appl Mater Interfaces 2021 Jul 1. Epub 2021 Jul 1.

Department of Chemistry, University of North Texas, 1508 West Mulberry Street, Denton, Texas 76201, United States.

An In(III) based metal-organic framework (MOF), In-pbpta, with topology was constructed from the trigonal prismatic [In(μ-O)(HO)(OC-)] secondary building unit (SBU) and a custom-designed tetratopic linker Hpbpta (pbpta = 4,4',4″,4‴-(1,4-phenylenbis(pyridine-4,2,6-triyl))-tetrabenzoic acid)). The obtained MOF shows a Brunauer-Emmett-Teller surface area of 1341 m/g with a pore volume of 0.64 cm/g, which is the highest among the scarcely reported In--MOFs. The constructed MOF demonstrates excellent performance as a heterogeneous Lewis acid catalyst for highly efficient conversion in a one-pot multicomponent Strecker reaction for the preparation of α-aminonitriles under solvent-free conditions, which can be easy to separate and recycle without significant loss of activity for up to seven cycles. The computational modeling studies suggest the presence of the three substrates in close vicinity to the In-oxo cluster. The strong interactions of the aldehyde/ketone and the amine with the In-oxo cluster together with the readily available cyanide ion around the In-oxo cluster lead to high catalytic conversion within a short period of time for the MOF catalyst. Our work therefore lays a foundation to develop MOF as a new class of efficient heterogeneous catalyst for one-pot Strecker reaction.
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http://dx.doi.org/10.1021/acsami.1c09074DOI Listing
July 2021

Porous Anionic Co(II) Metal-Organic Framework, with a High Density of Amino Groups, as a Superior Luminescent Sensor for Turn-on Al(III) Detection.

Chemistry 2021 Jun 10. Epub 2021 Jun 10.

Department of Chemistry, Indian Institute of Technology Kharagpur, Kharagpur, 721302, WB, India.

Accumulation of high concentrations of Al(III) in body has a direct impact on health and therefore, the trace detection of Al(III) has been a matter for substantial concern. An anionic metal organic framework ({[Me NH ] [Co(DATRz) (NH BDC)] ⋅ xG} ; 1; HDATRz=3,5-diamino-1,2,4-triazole, H NH -BDC=2-amino-1,4-benzenedicarboxylic acid, G=guest molecule) composed of two types of secondary building units (SBU) and channels of varying sizes was synthesized by employing a rational design mixed ligand synthesis approach. Free -NH groups on both the ligands are immobilized onto the pore surface of the MOF which acts as a superior luminescent sensor for turn-on Al(III) detection. Furthermore, the large channels could allow the counter-ions to pass through and get exchanged to selectively detect Al(III) in presence of other seventeen metal ions with magnificent luminescence enhancement. The observed limit of detection is as low as 17.5 ppb, which is the lowest among the MOF-based sensors achieved so far. To make this detection approach simple, portable and economic, we demonstrate MOF filter paper test for real time naked eye observation.
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http://dx.doi.org/10.1002/chem.202101692DOI Listing
June 2021

Synthesis, Characterization, and Antimicrobial Investigation of a Novel Chlorhexidine Cyclamate Complex.

Cryst Growth Des 2020 Aug 4;20(8):4991-4999. Epub 2020 May 4.

Colgate-Palmolive Company, 909 River Road, Piscataway, New Jersey 08854, United States.

The synthesis, crystal structure, and antimicrobial efficacy are reported for a novel material comprising a 1:2 ratio of chlorhexidine (CHX) to N-cyclohexylsulfamate (, artificial sweetener known as cyclamate). The chemical structure is unambiguously identified by incorporating a combination of single-crystal X-ray diffraction (SC-XRD), electrospray ionization mass spectrometry (ESI-MS), H nuclear magnetic resonance (NMR) spectroscopy, correlation spectroscopy (COSY), and attenuated total reflection Fourier-transform infrared spectroscopy (ATR-FTIR). The new material: 1) is amongst only several reported structures identified to date incorporating the vital chlorhexidine antimicrobial drug; 2) exhibits broad spectrum antimicrobial activity at concentrations less than 15 μg/mL; and 3) provides a unique delivery method for the essential active pharmaceutical ingredient (API). Furthermore, substitution of inactive gluconate with bioactive cyclamate counterion potentially provides the additional benefit of improving the taste profile of chlorhexidine.
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http://dx.doi.org/10.1021/acs.cgd.0c00107DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8159181PMC
August 2020

Imparting Ion Selectivity to Covalent Organic Framework Membranes Using Assembly for Blue Energy Harvesting.

J Am Chem Soc 2021 Jun 24;143(25):9415-9422. Epub 2021 May 24.

Zhejiang Provincial Key Laboratory of Advanced Chemical Engineering Manufacture Technology, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, China.

It has long been a challenge to fabricate angstrom-sized functional pores for mimicking the function of biological channels to afford selective transmembrane transport. In this study, we describe a facile strategy to incorporate ionic elements into angstrom-sized channels using encapsulation of charged dye molecules during the interface polymerization of a three-dimensional covalent organic framework (3D COF). We demonstrate that this approach is tailorable as it enables control over both the type and content of the guest and thus allows manipulation of the membrane function. The resulting membranes exhibit excellent permselectivity and low membrane resistance, thereby indicating the potential for harvesting salinity gradient (blue) energy. As a proof-of-concept study, the reverse electrodialysis device coupled with positive and negative dye encapsulated COF membranes afforded a power density of up to 51.4 W m by mixing the simulated seawater and river water, which far exceeds the commercialization benchmark (5 W m). We envision that this strategy will pave the way for constructing new multifunctional biomimetic systems.
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http://dx.doi.org/10.1021/jacs.1c02090DOI Listing
June 2021

A window-space-directed assembly strategy for the construction of supertetrahedron-based zeolitic mesoporous metal-organic frameworks with ultramicroporous apertures for selective gas adsorption.

Chem Sci 2021 Mar 5;12(16):5767-5773. Epub 2021 Mar 5.

Department of Chemistry, University of North Texas Denton 76201 USA

Despite their scarcity due to synthetic challenges, supertetrahedron-based metal-organic frameworks (MOFs) possess intriguing architectures, diverse functionalities, and superb properties that make them in-demand materials. Employing a new window-space-directed assembly strategy, a family of mesoporous zeolitic MOFs have been constructed herein from corner-shared supertetrahedra based on homometallic or heterometallic trimers [M(OH/O)(COO)] (M = Co, Ni or CoTi). These MOFs consisted of close-packed truncated octahedral cages possessing a sodalite topology and large β-cavity mesoporous cages (∼22 Å diameter) connected by ultramicroporous apertures (∼5.6 Å diameter). Notably, the supertetrahedron-based sodalite topology MOF combined with the CoTi trimer exhibited high thermal and chemical stability as well as the ability to efficiently separate acetylene (CH) from carbon dioxide (CO).
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http://dx.doi.org/10.1039/d0sc06841aDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8083976PMC
March 2021

Porous Covalent Organic Polymers for Efficient Fluorocarbon-Based Adsorption Cooling.

Angew Chem Int Ed Engl 2021 Aug 4;60(33):18037-18043. Epub 2021 Jun 4.

Energy and Environment Directorate, Pacific Northwest National Laboratory, Richland, WA, 99352, USA.

Adsorption-based cooling is an energy-efficient renewable-energy technology that can be driven using low-grade industrial waste heat and/or solar heat. Here, we report the first exploration of fluorocarbon adsorption using porous covalent organic polymers (COPs) for this cooling application. High fluorocarbon R134a equilibrium capacities and unique overall linear-shaped isotherms are revealed for the materials, namely COP-2 and COP-3. The key role of mesoporous defects on this unusual adsorption behavior was demonstrated by molecular simulations based on atomistic defect-containing models built for both porous COPs. Analysis of simulated R134a adsorption isotherms for various defect-containing atomistic models of the COPs shows a direct correlation between higher fluorocarbon adsorption capacities and increasing pore volumes induced by defects. Combined with their high porosities, excellent reversibility, fast kinetics, and large operating window, these defect-containing porous COPs are promising for adsorption-based cooling applications.
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http://dx.doi.org/10.1002/anie.202102337DOI Listing
August 2021

Highly Stable Single Crystals of Three-Dimensional Porous Oligomer Frameworks Synthesized under Kinetic Conditions.

Angew Chem Int Ed Engl 2021 Jun 28;60(26):14664-14670. Epub 2021 May 28.

Zhejiang Provincial Key Laboratory of Advanced Chemical Engineering Manufacture Technology, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, China.

Various robust, crystalline, and porous organic frameworks based on in situ-formed imine-linked oligomers were investigated. These oligomers self-assembled through collaborative intermolecular hydrogen bonding interactions via liquid-liquid interfacial reactions. The soluble oligomers were kinetic products with multiple unreacted aldehyde groups that acted as hydrogen bond donors and acceptors and directed the assembly of the resulting oligomers into 3D frameworks. The sequential formation of robust covalent linkages and highly reversible hydrogen bonds enforced long-range symmetry and facilitated the production of large single crystals, with structures that were unambiguously determined by single-crystal X-ray diffraction. The unique hierarchical arrangements increased the steric hindrance of the imine bond, which prevented attacks from water molecules, greatly improving the stability. The multiple binding sites in the frameworks enabled rapid sequestration of micropollutant in water.
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http://dx.doi.org/10.1002/anie.202103729DOI Listing
June 2021

Efficient Electron Transfer from Electron-Sponge Polyoxometalate to Single-Metal Site Metal-Organic Frameworks for Highly Selective Electroreduction of Carbon Dioxide.

Small 2021 Apr 4:e2100762. Epub 2021 Apr 4.

Department of Chemistry, University of North Texas, 1508 W. Mulberry St., Denton, TX, 76201, USA.

In this work, by combining the superiority of polyoxometalates (POMs) and catalytic single-metal site Co of metalloporphyrin, a series of mixed-valence POM-based metal-organic frameworks (MOFs) composites is synthesized by a post-modification method. The electron-transfer property of [email protected](Co) composite is significantly enhanced owing to the directional electron-transfer from POM to single-metal site Co in PCN-222(Co). In particular, [email protected](Co) gives a high Faradaic efficiency of 96.2% for electroreduction of CO into CO and good stability over 10 h. DFT calculations confirm that the directional electron transfer, which accelerates the multi-electron transfer from the electrode to active single-metal site Co, enriches the electron density of the Co center, and ultimately reduces the energy of the rate-determining step, thus increasing the catalytic activity of CO reduction reaction (CO RR). This work therefore suggests some new insight for the design of efficient electrocatalysts for CO RR.
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http://dx.doi.org/10.1002/smll.202100762DOI Listing
April 2021

Green synthesis of olefin-linked covalent organic frameworks for hydrogen fuel cell applications.

Nat Commun 2021 Mar 31;12(1):1982. Epub 2021 Mar 31.

State Key Laboratory of Medicinal Chemical Biology, College of Chemistry, Nankai University, Tianjin, China.

Green synthesis of crystalline porous materials for energy-related applications is of great significance but very challenging. Here, we create a green strategy to fabricate a highly crystalline olefin-linked pyrazine-based covalent organic framework (COF) with high robustness and porosity under solvent-free conditions. The abundant nitrogen sites, high hydrophilicity, and well-defined one-dimensional nanochannels make the resulting COF an ideal platform to confine and stabilize the HPO network in the pores through hydrogen-bonding interactions. The resulting material exhibits low activation energy (E) of 0.06 eV, and ultrahigh proton conductivity across a wide relative humidity (10-90 %) and temperature range (25-80 °C). A realistic proton exchange membrane fuel cell using the olefin-linked COF as the solid electrolyte achieve a maximum power of 135 mW cm and a current density of 676 mA cm, which exceeds all reported COF materials.
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http://dx.doi.org/10.1038/s41467-021-22288-9DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8012354PMC
March 2021

Covalent organic framework nanofluidic membrane as a platform for highly sensitive bionic thermosensation.

Nat Commun 2021 03 23;12(1):1844. Epub 2021 Mar 23.

Zhejiang Provincial Key Laboratory of Advanced Chemical Engineering Manufacture Technology, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, China.

Thermal sensation, which is the conversion of a temperature stimulus into a biological response, is the basis of the fundamental physiological processes that occur ubiquitously in all organisms from bacteria to mammals. Significant efforts have been devoted to fabricating artificial membranes that can mimic the delicate functions of nature; however, the design of a bionic thermometer remains in its infancy. Herein, we report a nanofluidic membrane based on an ionic covalent organic framework (COF) that is capable of intelligently monitoring temperature variations and expressing it in the form of continuous potential differences. The high density of the charged sites present in the sub-nanochannels renders superior permselectivity to the resulting nanofluidic system, leading to a high thermosensation sensitivity of 1.27 mV K, thereby outperforming any known natural system. The potential applicability of the developed system is illustrated by its excellent tolerance toward a broad range of salt concentrations, wide working temperatures, synchronous response to temperature stimulation, and long-term ultrastability. Therefore, our study pioneers a way to explore COFs for mimicking the sophisticated signaling system observed in the nature.
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http://dx.doi.org/10.1038/s41467-021-22141-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7988099PMC
March 2021

3D Cationic Polymeric Network Nanotrap for Efficient Collection of Perrhenate Anion from Wastewater.

Small 2021 Mar 21:e2007994. Epub 2021 Mar 21.

Department of Chemistry, University of North Texas, Denton, TX, 76201, USA.

Rhenium is one of the most valuable elements found in nature, and its capture and recycle are highly desirable for resource recovery. However, the effective and efficient collection of this material from industrial waste remains quite challenging. Herein, a tetraphenylmethane-based cationic polymeric network (CPN-tpm) nanotrap is designed, synthesized, and evaluated for ReO recovery. 3D building units are used to construct imidazolium salt-based polymers with positive charges, which yields a record maximum uptake capacity of 1133 mg g for ReO collection as well as fast kinetics ReO uptake. The sorption equilibrium is reached within 20 min and a k value of 8.5 × 10 mL g is obtained. The sorption capacity of CPN-tpm remains stable over a wide range of pH values and the removal efficiency exceeds 60% for pH levels below 2. Moreover, CPN-tpm exhibits good recyclability for at least five cycles of the sorption-desorption process. This work provides a new route for constructing a kind of new high-performance polymeric material for rhenium recovery and rhenium-contained industrial wastewater treatment.
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http://dx.doi.org/10.1002/smll.202007994DOI Listing
March 2021

Nanospace Engineering of Metal-Organic Frameworks through Dynamic Spacer Installation of Multifunctionalities for Efficient Separation of Ethane from Ethane/Ethylene Mixtures.

Angew Chem Int Ed Engl 2021 Apr 10;60(17):9680-9685. Epub 2021 Mar 10.

Department of Chemistry, University of North Texas CHEM 305D, 1508 W Mulberry St, Denton, TX, 76201, USA.

Herein, a dynamic spacer installation (DSI) strategy has been implemented to construct a series of multifunctional metal-organic frameworks (MOFs), LIFM-61/31/62/63, with optimized pore space and pore environment for ethane/ethylene separation. In this respect, a series of linear dicarboxylic acids were deliberately installed in the prototype MOF, LIFM-28, leading to a dramatically increased pore volume (from 0.41 to 0.82 cm  g ) and reduced pore size (from 11.1×11.1 Å to 5.6×5.6 Å ). The increased pore volume endows the multifunctional MOFs with much higher ethane adsorption capacity, especially for LIFM-63 (4.8 mmol g ), representing nearly three times as much ethane as the prototypical counterpart (1.7 mmol g ) at 273 K and 1 bar. Meanwhile, the reduced pore size imparts enhanced ethane/ethylene selectivity of the multifunctional MOFs. Theoretical calculations and dynamic breakthrough experiments confirm that the DSI is a promising approach for the rational design of multifunctional MOFs for this challenging task.
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http://dx.doi.org/10.1002/anie.202100114DOI Listing
April 2021

Spatial Engineering Direct Cooperativity between Binding Sites for Uranium Sequestration.

Adv Sci (Weinh) 2021 Jan 4;8(2):2001573. Epub 2020 Dec 4.

Department of Chemistry University of South Florida 4202 E. Fowler Avenue Tampa FL 33620 USA.

Preorganization is a basic design principle used by nature that allows for synergistic pathways to be expressed. Herein, a full account of the conceptual and experimental development from randomly distributed functionalities to a convergent arrangement that facilitates cooperative binding is given, thus conferring exceptional affinity toward the analyte of interest. The resulting material with chelating groups populated adjacently in a spatially locked manner displays up to two orders of magnitude improvement compared to a random and isolated manner using uranium sequestration as a model application. This adsorbent shows exceptional extraction efficiencies, capable of reducing the uranium concentration from 5 ppm to less than 1 ppb within 10 min, even though the system is permeated with high concentrations of competing ions. The efficiency is further supported by its ability to extract uranium from seawater with an uptake capability of 5.01 mg g, placing it among the highest-capacity seawater uranium extraction materials described to date. The concept presented here uncovers a new paradigm in the design of efficient sorbent materials by manipulating the spatial distribution to amplify the cooperation of functions.
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http://dx.doi.org/10.1002/advs.202001573DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7816700PMC
January 2021

A MOF-based Ultra-Strong Acetylene Nano-trap for Highly Efficient C H /CO Separation.

Angew Chem Int Ed Engl 2021 Mar 4;60(10):5283-5288. Epub 2021 Feb 4.

Department of Chemistry, University of North Texas, Denton, TX, 76201, USA.

Porous materials with open metal sites have been investigated to separate various gas mixtures. However, open metal sites show the limitation in the separation of some challenging gas mixtures, such as C H /CO . Herein, we propose a new type of ultra-strong C H nano-trap based on multiple binding interactions to efficiently capture C H molecules and separate C H /CO mixture. The ultra-strong acetylene nano-trap shows a benchmark Q of 79.1 kJ mol for C H , a record high pure C H uptake of 2.54 mmol g at 1×10  bar, and the highest C H /CO selectivity (53.6), making it as a new benchmark material for the capture of C H and the separation of C H /CO . The locations of C H molecules within the MOF-based nanotrap have been visualized by the in situ single-crystal X-ray diffraction studies, which also identify the multiple binding sites accountable for the strong interactions with C H .
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http://dx.doi.org/10.1002/anie.202016225DOI Listing
March 2021

Rational Construction of Borromean Linked Crystalline Organic Polymers.

Angew Chem Int Ed Engl 2021 Feb 28;60(6):2974-2979. Epub 2020 Dec 28.

State Key Laboratory of Medicine Chemistry Biology, College of Chemistry, Nankai University, Tianjin, 300071, China.

Attributed to the unique topological complexity and elegant beauty, Borromean systems are attracting intense attention. However, at present, the construction of Borromean linked organic polymers remains a challenge. To address this formidable challenge, we developed a supramolecular-synthon-driven approach to fabricate Borromean linked organic polymer. The solvothermal condensation reaction of a judiciously selected trigonal pyramidal building block, 1,3,5-Tris(4-aminophenyl)adamantane, with linear dialdehyde building blocks allowed the construction of two rare covalent organic frameworks (COFs) with high crystallinity and robustness. Structure refinement unveiled the successful formation of entangled 2D→2D Borromean arrayed structures. Both the two COFs were of microporosity and thus demonstrated the potentials for gas separation. The successful synthesis of the first two Borromean linked organic polymers paves the avenue to expand the supramolecular-synthon-driven approach to other building blocks and topologies, and broadens the family and scope of COFs.
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http://dx.doi.org/10.1002/anie.202012504DOI Listing
February 2021

Efficient separation of xylene isomers by a guest-responsive metal-organic framework with rotational anionic sites.

Nat Commun 2020 Oct 28;11(1):5456. Epub 2020 Oct 28.

Key Laboratory of Biomass Chemical Engineering of Ministry of Education, College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, China.

The separation of xylene isomers (para-, meta-, orth-) remains a great challenge in the petrochemical industry due to their similar molecular structure and physical properties. Porous materials with sensitive nanospace and selective binding sites for discriminating the subtle structural difference of isomers are urgently needed. Here, we demonstrate the adaptively molecular discrimination of xylene isomers by employing a NbOF-pillared metal-organic framework (NbOFFIVE-bpy-Ni, also referred to as ZU-61) with rotational anionic sites. Single crystal X-ray diffraction studies indicate that ZU-61 with guest-responsive nanospace/sites can adapt the shape of specific isomers through geometric deformation and/or the rotation of fluorine atoms in anionic sites, thereby enabling ZU-61 to effectively differentiate xylene isomers through multiple C-H···F interactions. ZU-61 exhibited both high meta-xylene uptake capacity (3.4 mmol g) and meta-xylene/para-xylene separation selectivity (2.9, obtained from breakthrough curves), as well as a favorable separation sequence as confirmed by breakthrough experiments: para-xylene elute first with high-purity (≥99.9%), then meta-xylene, and orth-xylene. Such a remarkable performance of ZU-61 can be attributed to the type anionic binding sites together with its guest-response properties.
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http://dx.doi.org/10.1038/s41467-020-19209-7DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7595167PMC
October 2020

COF-inspired fabrication of two-dimensional polyoxometalate based open frameworks for biomimetic catalysis.

Nanoscale 2020 Nov 15;12(41):21218-21224. Epub 2020 Oct 15.

State Key Laboratory of Medicinal Chemical Biology, College of Chemistry, Nankai University, Tianjin 300071, China.

The development of highly efficient and robust biomimetic catalysts is an essential and feasible strategy to overcome the intrinsic drawbacks of natural enzymes. Inspired by the synthetic strategy of covalent organic frameworks, we adopted a covalent-bond-driven strategy to prepare polyoxometalate (POM) based open frameworks (NKPOM-OFs = Nankai University POM-OFs) with abundant Mo[double bond, length as m-dash]O groups that can mimic the active center of sulfite oxidase. Four 2-dimensional (2D) NKPOM-OFs were designed and synthesized via the condensation reaction of linear amino-containing POMs with planar tetra-aldehyde monomers. Benefitting from the high crystallinity, the structures of 2D POM-OFs can be successfully determined from structural simulations. The results unveiled that NKPOM-OFs possessed 2D staggered stacking layered structures with the sql topology. All these NKPOM-OFs exhibited high crystallinity and stability and demonstrated outstanding performance to serve as biomimetic catalysts of sulfite oxidase with good recyclability. Notably, exfoliation of NKPOM-OFs under ultrasonic treatment can significantly boost the catalytic activity with almost two times faster reaction rates. This study not only enriches the facile and versatile synthesis strategy for POM-OFs but also provides new biomimetic platforms for biocatalysis.
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http://dx.doi.org/10.1039/d0nr05662fDOI Listing
November 2020

Metal-Organic Frameworks for Enzyme Immobilization: Beyond Host Matrix Materials.

ACS Cent Sci 2020 Sep 27;6(9):1497-1506. Epub 2020 Aug 27.

Department of Chemistry, University of North Texas, 1508 West Mulberry Street, Denton, Texas 76201, United States.

Enzyme immobilization in metal-organic frameworks (MOFs) as a promising strategy is attracting the interest of scientists from different disciplines with the expansion of MOFs' development. Different from other traditional host materials, their unique strengths of high surface areas, large yet adjustable pore sizes, functionalizable pore walls, and diverse architectures make MOFs an ideal platform to investigate hosted enzymes, which is critical to the industrial and commercial process. In addition to the protective function of MOFs, the extensive roles of MOFs in the enzyme immobilization are being well-explored by making full use of their remarkable properties like well-defined structure, high porosity, and tunable functionality. Such development shifts the focus from the exploration of immobilization strategies toward functionalization. Meanwhile, this would undoubtedly contribute to a better understanding of enzymes in regards to the structural transformation after being hosted in a confinement environment, particularly to the orientation and conformation change as well as the interplay between enzyme and matrix MOFs. In this Outlook, we target a comprehensive review of the role diversities of the host matrix MOF based on the current enzyme immobilization research, along with proposing an outlook toward the future development of this field, including the representatives of potential techniques and methodologies being capable of studying the hosted enzymes.
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http://dx.doi.org/10.1021/acscentsci.0c00687DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7517118PMC
September 2020

Exploration of advanced porous organic polymers as a platform for biomimetic catalysis and molecular recognition.

Chem Commun (Camb) 2020 Sep;56(73):10631-10641

College of Chemical and Biological Engineering, Zhejiang University, Hangzhou, 310027, China.

Nature has long been a dominant source of inspiration in the area of chemistry, serving as prototypes for the design of materials with proficient performance. In this Feature article, we present our efforts to explore porous organic polymers (POPs) as a platform for the construction of biomimetic materials to enable new technologies to achieve efficient conversions and molecular recognition. For each aspect, we first present the chemical basis of nature, followed by depicting the principles and design strategies involved for functionalizing POPs along with a summary of critical requirements for materials, culminating in a demonstration of unique features of POPs. Our endeavours in using POPs to address the fundamental scientific problems related to biomimetic catalysis and adsorption are then illustrated to show their enormous potential and capabilities for applications ranging from concerted catalysis to radionuclide sequestration. To conclude, we present a personal perspective on the challenges and opportunities in this emerging field.
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http://dx.doi.org/10.1039/d0cc04351fDOI Listing
September 2020

Single-Pore versus Dual-Pore Bipyridine-Based Covalent-Organic Frameworks: An Insight into the Heterogeneous Catalytic Activity for Selective CH Functionalization.

Small 2021 Jun 11;17(22):e2003970. Epub 2020 Sep 11.

Department of  Chemistry, University of South Florida, 4202 E. Fowler Avenue, Tampa, FL, 33620, USA.

Exponential growth in the field of covalent-organic frameworks (COFs) is emanating from the direct correlation between designing principles and desired properties. The comparison of catalytic activity between single-pore and dual-pore COFs is of importance to establish structure-function relationship. Herein, the synthesis of imine-linked dual-pore [(BPyDC)] -ETTA COFs (x = 0%, 25%, 50%, 75%, 100%) with controllable bipyridine content is fulfilled by three-component condensation of 4,4',4″,4'″-(ethene-1,1,2,2-tetrayl)tetraaniline (ETTA), 4,4'-biphenyldialdehyde, and 2,2'-bipyridyl-5,5'-dialdehyde in different stoichiometric ratio. The strong coordination of bipyridine moieties of [(BPyDC)] -ETTA COFs with palladium imparts efficient catalytic active sites for selective functionalization of sp CH bond to CX (X = Br, Cl) or CO bonds in good yield. To broaden the scope of regioselective CH functionalization, a wide range of electronically and sterically substituted substrates under optimized catalytic condition are investigated. A comparison of the catalytic activity of palladium decorated dual-pore frameworks with single-pore imine-linked Pd(II) @ Py-2,2'-BPyDC framework  is undertaken. The finding of this work provides a sporadic example of chelation-assisted CH functionalization and disclosed an in-depth comparison of the relationship between superior catalytic activity and core properties of rationally designed imine linked frameworks.
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http://dx.doi.org/10.1002/smll.202003970DOI Listing
June 2021

The first ternary Nd-MOF/GO/FeO nanocomposite exhibiting an excellent photocatalytic performance for dye degradation.

Dalton Trans 2020 Aug;49(31):10745-10754

Department of Chemistry, University of South Florida, 4202 Easter Fowler Avenue, Tampa, Florida 33620, USA.

Herein, a ternary nanocomposite photocatalyst (MOF-1/GO/Fe3O4) based on a novel Nd-MOF, graphene oxide (GO), and Fe3O4 was successfully prepared. It was verified that the MOF nanoparticles and GO sheets were integrated by means of intimate interfacial contacts and a large number of Fe3O4 microspheres were uniformly loaded on the surface of GO. The ternary nanocomposite was a stable, environmentally friendly, and efficient visible-light photocatalyst, which displayed excellent photocatalytic performance in the degradation of methylene blue (MB) (∼95%) dye within 80 min under sunlight irradiation in the aqueous solution. Compared to MOF-1, the photocatalytic efficiency of the composite was improved by 90% and the excitation wavelength was moved from the ultraviolet to visible region. The enhancement of photocatalytic performance can be ascribed to the introduction of GO, which efficiently accelerated electron migration, minimized the recombination of photogenerated electron-hole pairs, and improved the optical absorption properties, leading to a synergistic facilitation of the photocatalysis process. The ternary composite demonstrated excellent stability and reusability and can be easily recovered by a magnetic field. The study would provide novel avenues for the preparation of highly efficient and environmentally stable photocatalysts for organic wastewater treatment.
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http://dx.doi.org/10.1039/d0dt01648aDOI Listing
August 2020

A Mixed-Metal Porphyrinic Framework Promoting Gas-Phase CO Photoreduction without Organic Sacrificial Agents.

ChemSusChem 2020 Dec 24;13(23):6273-6277. Epub 2020 Aug 24.

Department of Chemistry, University of North Texas, 1508 W Mulberry St, Denton, TX 76201, United States.

A photoactive porphyrinic metal-organic framework (MOF) has been prepared by exchanging Ti into a Zr-based MOF precursor. The resultant mixed-metal Ti/Zr porphyrinic MOF demonstrates much-improved efficiency for gas-phase CO photoreduction into CH and CO under visible-light irradiation using water vapor compared to the parent Zr-MOF. Insightful studies have been conducted to probe the photocatalysis processes. This work provides the first example of gas-phase CO photoreduction into methane without organic sacrificial agents on a MOF platform, thereby paving an avenue for developing MOF-based photocatalysts for application in CO photoreduction and other types of photoreactions.
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http://dx.doi.org/10.1002/cssc.202001610DOI Listing
December 2020

Secondary Sphere Effects on Porous Polymeric Organocatalysts for CO Transformations: Subtle Modifications Resulting in Superior Performance.

ACS Appl Mater Interfaces 2020 Jul 8;12(29):32827-32833. Epub 2020 Jul 8.

Department of Chemistry, University of South Florida, 4202 East Fowler Avenue, Tampa, Florida 33620, United States.

Albeit harnessing secondary sphere interactions to exert control over the reaction outcomes has primarily been applied to enzymatic and organometallic catalysis, there are seldom any studies that introduce outer-sphere modifiers into organocatalysts. This is even less in the corresponding heterogeneous catalytic system. In this contribution, we experimentally and computationally investigate the role of secondary effects in the reactivity of bromide anions toward CO transformations. Six pyridinium cationic porous frameworks have been synthesized and fully characterized. Structure-activity relationships and kinetics show that the type and the location of the substituents on the cationic framework have a significant impact on the nucleophilic reactivity of their bromide counter anion. Specifically, the attachment of amine substituent to the ortho position relative to a pyridinium motif produces a remarkably efficient catalyst for CO transformation, by a factor of six times greater in comparison to the pristine pyridinium-based polymer. The hydrogen-bond-interaction-promoted reagent activation and enhanced delocalization ability of bromide counter anion are believed to be the key to driving the reaction toward CO utilization. These observations, therefore, champion the leverage of secondary interaction for optimizing the reactivity of organocatalysts.
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http://dx.doi.org/10.1021/acsami.0c08817DOI Listing
July 2020

Metal-Organic Framework Disintegrants: Enzyme Preparation Platforms with Boosted Activity.

Angew Chem Int Ed Engl 2020 09 20;59(38):16764-16769. Epub 2020 Jul 20.

State Key Laboratory of Medicinal Chemical Biology, College of Pharmacy, Nankai University, Tianjin, 300071, China.

An enzyme formulation using customized enzyme activators (metal ions) to directly construct metal-organic frameworks (MOFs) as enzyme protective carriers is presented. These MOF carriers can also serve as the disintegrating agents to simultaneously release enzymes and their activators during biocatalysis with boosted activities. This highly efficient enzyme preparation combines enzyme immobilization (enhanced stability, easy operation) and homogeneous biocatalysis (fast diffusion, high activity). The MOF serves as an ion pump that continuously provides metal ion activators that greatly promote the enzymatic activities (up to 251 %). This MOF-enzyme composite demonstrated an excellent protective effect against various perturbation environments. A mechanistic investigation revealed that the spontaneous activator/enzyme release and ion pumping enable enzymes to sufficiently interact with their activators owing to the proximity effects, leading to a boost in biocatalytic performance.
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http://dx.doi.org/10.1002/anie.202007827DOI Listing
September 2020

Fabrication of Photoresponsive Crystalline Artificial Muscles Based on PEGylated Covalent Organic Framework Membranes.

ACS Cent Sci 2020 May 21;6(5):787-794. Epub 2020 Apr 21.

State Key Laboratory of Medicinal Chemical Biology, College of Chemistry, Nankai University, Tianjin 300071, China.

Seeking new photoresponsive materials with high energy conversion efficiency, good mechanical properties, as well as well-defined photoactuation mechanisms is of paramount significance. To address these challenges, we first introduced crystalline covalent organic frameworks (COFs) into the photoactuator field and created a facile fabrication strategy to directly install photoresponsive functional groups (i.e., acylhydrazone) on the skeletons of COFs. Herein, an approach to use polyethylene glycol (PEG) cross-linked dimers as the building blocks of the platform was developed and afforded a series of uniform and freestanding membranes () with outstanding mechanical properties (e.g., high flexibility and mechanical strength). Notably, these membranes possessed a fast mechanical response (e.g., bending) to UV light and good reversibility upon blue light or heating. After an in-depth investigation of the photoactuation mechanism via various techniques, we proposed a mechanism for the photoresponsive performance of : configurational change of acylhydrazone (i.e., E ↔ Z isomerization) accompanied by an excited-state intramolecular proton transfer (ESIPT) process intramolecularly transferring hydrogens from hydrogen donors (N-H) to hydrogen acceptors (oxygen in PEG). Moreover, attributed to the PEG moieties, also demonstrated a vapor-responsive performance. This study not only broadens the application scopes of COFs but also provides new opportunities for the construction of multi-stimuli-responsive materials.
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http://dx.doi.org/10.1021/acscentsci.0c00260DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7256951PMC
May 2020

Synthesis, Characterization, and Investigation of the Antimicrobial Activity of Cetylpyridinium Tetrachlorozincate.

ACS Omega 2020 May 28;5(18):10359-10365. Epub 2020 Apr 28.

Colgate-Palmolive Company, 909 River Road, Piscataway, New Jersey 08854, United States.

Cetylpyridinium tetrachlorozincate (referred to herein as (CP)ZnCl) was synthesized and its solid-state structure was elucidated single-crystal X-ray diffraction (SC-XRD), revealing a stoichiometry of CHClNZn with two cetylpyridinium (CP) cations per [ZnCl] tetrahedra. Crystal structures at 100 and 298 K exhibited a zig-zag pattern with alternating alkyl chains and zinc units. The material showed potential for application as a broad-spectrum antimicrobial agent, to reduce volatile sulfur compounds (VSCs) generated by bacteria, and in the fabrication of advanced functional materials. Minimum inhibitory concentration (MIC) of (CP)ZnCl was 60, 6, and 6 μg mL for , , and , respectively. The MIC values of (CP)ZnCl were comparable to that of pure cetylpyridinium chloride (CPC), despite the fact that approximately 16% of the bactericidal CPC is replaced with bacteriostatic ZnCl in the structure. A modified layer-by-layer deposition technique was implemented to synthesize mesoporous silica (., SBA-15) loaded with approximately 9.0 wt % CPC and 8.9 wt % Zn.
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http://dx.doi.org/10.1021/acsomega.0c00131DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7226859PMC
May 2020

A Porous Organic Polymer Nanotrap for Efficient Extraction of Palladium.

Angew Chem Int Ed Engl 2020 Oct 9;59(44):19618-19622. Epub 2020 Jun 9.

Department of Chemistry, University of South Florida, 4202 E Fowler Ave., Tampa, FL, 33620, USA.

To offset the environmental impact of platinum-group element (PGE) mining, recycling techniques are being explored. Porous organic polymers (POPs) have shown significant promise owing to their selectivity and ability to withstand harsh conditions. A series of pyridine-based POP nanotraps, POP-Py, POP-pNH -Py, and POP-oNH -Py, have been designed and systematically explored for the capture of palladium, one of the most utilized PGEs. All of the POP nanotraps demonstrated record uptakes and rapid capture, with the amino group shown to be vital in improving performance. Further testing on the POP nanotrap regeneration and selectivity found that POP-oNH -Py outperformed POP-pNH -Py. Single-crystal X-ray analysis indicated that POP-oNH -Py provided a stronger complex compared to POP-pNH -Py owing to the intramolecular hydrogen bonding between the amino group and coordinated chlorine molecules. These results demonstrate how slight modifications to adsorbents can maximize their performance.
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http://dx.doi.org/10.1002/anie.202006596DOI Listing
October 2020

Tailored Porous Organic Polymers for Task-Specific Water Purification.

Acc Chem Res 2020 04 13;53(4):812-821. Epub 2020 Apr 13.

Department of Chemistry, University of South Florida, Tampa, Florida 33620, United States.

The Industrial Revolution has resulted in social and economic improvements, but unfortunately, with the development of manufacturing and mining, water sources have been pervaded with contaminants, putting Earth's freshwater supply in peril. Therefore, the segregation of pollutants-such as radionuclides, heavy metals, and oil spills-from water streams, has become a pertinent problem. Attempts have been made to extract these pollutants through chemical precipitation, sorbents, and membranes. The limitations of the current remediation methods, including the generation of a considerable volume of chemical sludge as well as low uptake capacity and/or selectivity, actuate the need for materials innovation. These insufficiencies have provoked our interest in the exploration of porous organic polymers (POPs) for water treatment. This category of porous material has been at the forefront of materials research due to its modular nature, , its tunable functionality and tailorable porosity. Compared to other materials, the practicality of POPs comes from their purely organic composition, which lends to their stability and ease of synthesis. The potential of using POPs as a design platform for solid extractors is closely associated with the ease with which their pore space can be functionalized with high densities of strong adsorption sites, resulting in a material that retains its robustness while providing specified interactions depending on the contaminant of choice.POPs raise opportunities to improve current or enable new technologies to achieve safer water. In this Account, we describe some of our efforts toward the exploitation of the unique properties of POPs for improving water purification by answering key questions and proposing research opportunities. The design strategies and principles involved for functionalizing POPs include the following: increasing the density and flexibility of the chelator to enhance their cooperation, introducing the secondary sphere modifiers to reinforce the primary binding, and enforcing the orientation of the ligands in the pore channel to increase the accessibility and cooperation of the functionalities. For each strategy, we first describe its chemical basis, followed by presenting examples that convey the underlying concepts, giving rise to functional materials that are beyond the traditional ones, as demonstrated by radionuclide sequestration, heavy metal decontamination, and oil-spill cleanup. Our endeavors to explore the applicability of POPs to deal with these high-priority contaminants are expected to impact personal consumer water purifiers, industrial wastewater management systems, and nuclear waste management. In our view, more exciting will be new applications and new examples of the functionalization strategies made by creatively merging the strategies mentioned above, enabling increasingly selective binding and efficiency and ultimately promoting POPs for practical applications to enhance water security.
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http://dx.doi.org/10.1021/acs.accounts.0c00007DOI Listing
April 2020

[email protected]/PVDF Nanocomposite Membrane for Efficient Pervaporation Desulfurization via a Layer-by-Layer Technology.

ACS Appl Mater Interfaces 2020 May 9;12(18):20664-20671. Epub 2020 Apr 9.

Department of Chemistry, University of South Florida, 4202 E, Fowler Avenue, Tampa, Florida 33620, United States.

The desulfurization property of conventional mixed matrix membranes (MMMs) cannot meet the necessary demand due to particles aggregation and interface defects. Here, we put forward a layer-by-layer (LBL) approach to make a novel [email protected]/poly(vinylidene difluoride)(PVDF) composite membrane for pervaporation desulfurization. In this way, a ZIF-8 layer is covered on the surface of the PVDF porous membrane via an in situ growth method. Then, a PEG layer is covered on the ZIF-8 layer by a casting method. Compared with pristine PEG membranes, the separation performance of the [email protected]/PVDF nanocomposite membrane increased significantly. This can be attributed to the homogeneous ZIF-8 particle layer and better compatibility between the poly(ethylene glycol) (PEG) matrix and ZIF-8 particles. The membrane achieves a maximum total flux of 3.08 kg·m·h at the third in situ growth cycles of ZIF-8 particles and a maximum sulfur enrichment factor of 7.6 at the sixth in situ growth cycles of ZIF-8 particles.
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http://dx.doi.org/10.1021/acsami.0c02513DOI Listing
May 2020

Fabricating Covalent Organic Framework Capsules with Commodious Microenvironment for Enzymes.

J Am Chem Soc 2020 04 30;142(14):6675-6681. Epub 2020 Mar 30.

State Key Laboratory of Medicinal Chemical biology, College of Pharmacy, Nankai University, Tianjin 300071, China.

Enzyme immobilization has been demonstrated to be a favorable protocol to promote industrialization of biomacromolecules. Despite tremendous efforts to develop new strategies and materials to realize this process, maintaining enzyme activity is still a formidable challenge. Herein we created a sacrificial templating method, using metal-organic frameworks (MOFs) as sacrificial templates to construct hollow covalent organic framework (COF) capsules for enzyme encapsulation. This strategy can provide a capacious microenvironment to unleash enzyme molecules. The improved conformational freedom of enzymes, enhanced mass transfer, and protective effect against the external environment ultimately boosted the enzymatic activities. We also found that this strategy possesses high versatility that is suitable for diverse biomacromolecules, MOF templates, and COF capsules. Moreover, the dimensions, pore sizes, and shell thickness of COF capsules can be conveniently tuned, allowing for customizing bioreactors for specific functions. For example, coencapsulation of different enzymes with synergistic functions were successfully demonstrated using this bioreactor platform. This study not only opens up a new avenue to overcome the present limitations of enzymatic immobilization in porous matrixes but also provides new opportunities for construction of biomicrodevices or artificial organelles based on crystalline porous materials.
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http://dx.doi.org/10.1021/jacs.0c00285DOI Listing
April 2020
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