Publications by authors named "Pengfei Ji"

33 Publications

Self-adaptive cardiac optogenetics device based on negative stretching-resistive strain sensor.

Sci Adv 2021 Nov 24;7(48):eabj4273. Epub 2021 Nov 24.

National Key Laboratory of Science and Technology on Micro/Nano Fabrication, Shanghai Jiao Tong University, Shanghai 200240, China.

[Figure: see text].
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http://dx.doi.org/10.1126/sciadv.abj4273DOI Listing
November 2021

Molecular dynamics study on the diffusion process of AuAgCuNiPd high-entropy alloy metallurgy induced by pulsed laser heating.

Phys Chem Chem Phys 2021 Sep 15;23(35):19482-19493. Epub 2021 Sep 15.

Laser Micro/Nano Fabrication Laboratory, School of Mechanical Engineering, Beijing Institute of Technology, Beijing 100081, People's Republic of China.

As novel alloy materials with outstanding mechanical properties, high-entropy alloys have a wide range of promising applications. By establishing individual Au, Ag, Cu, Ni, and Pd nanolaminates with face-centered-cubic lattice structure arrangements, molecular dynamics simulation is carried out to track the diffusion process of AuAgCuNiPd high-entropy alloy metallurgy, which is induced by pulsed laser heating. The temperature, potential energy, and kinetic energy are analyzed to evaluate the metallurgy. The snapshots and atomic fractions are presented to show the mass transfer between metallic nanolaminates. The diffusion process is firstly observed 0.3 ns after the central point for pulsed laser heating (absorbed laser energy density at 7 kJ cm and pulse duration of 0.5 ns). Meanwhile, the degrees of atomic activity for Au, Ag, Cu, Ni, and Pd are assessed by calculating the mean square displacement and diffusion coefficient. Ni has a slightly larger diffusion coefficient than the other four metallic elements. Moreover, after the central point of laser irradiation, the kinetic energy of the system reduces, while the potential energy increases, which relates to the transition from nanolaminates to high-entropy alloys. A critical absorbed laser energy density of 6 kJ cm with a relative error of 8.3% for the generation of AuAgCuNiPd high-entropy alloys is found. The order of constituent nanolaminates configured with the earlier initiation of diffusion between atoms in the neighboring nanolaminates speeds up the metallurgy.
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http://dx.doi.org/10.1039/d1cp02181hDOI Listing
September 2021

Excitation of ultraviolet range Dirac-type plasmon resonance with an ultra-high Q-factor in the topological insulator BiSbTeSe nanoshell.

Opt Express 2021 Mar;29(6):9252-9260

Excitation of ultraviolet (UV) range plasmon resonance with high quality (Q)-factor has been significantly challenging in plasmonics because of inherent limitations in metals like Au and Ag. Herein, we theoretically investigated UV-visible range plasmons in the topological insulator BiSbTeSe (BSTS) nanosphere and nanoshell. In contrast to broad linewidth plasmon absorptions in the BSTS nanospheres, an ultra-sharp absorption peak with the Q-factor as high as 52 is excited at UV frequencies in the BSTS nanoshells. This peak is attributed to Dirac-type plasmon resonance originating from massless Dirac carriers in surface states of the BSTS. Furthermore, a tunable plasmon wavelength of the resonance is demonstrated by varying geometrical parameters of the BSTS nanoshells. This may find applications in surface enhanced Raman spectroscopies, nanolasers and biosensors in the UV regions.
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http://dx.doi.org/10.1364/OE.418514DOI Listing
March 2021

Abiotic reduction of ketones with silanes catalysed by carbonic anhydrase through an enzymatic zinc hydride.

Nat Chem 2021 04 18;13(4):312-318. Epub 2021 Feb 18.

Department of Chemistry, University of California, Berkeley, CA, USA.

Enzymatic reactions through mononuclear metal hydrides are unknown in nature, despite the prevalence of such intermediates in the reactions of synthetic transition-metal catalysts. If metalloenzymes could react through abiotic intermediates like these, then the scope of enzyme-catalysed reactions would expand. Here we show that zinc-containing carbonic anhydrase enzymes catalyse hydride transfers from silanes to ketones with high enantioselectivity. We report mechanistic data providing strong evidence that the process involves a mononuclear zinc hydride. This work shows that abiotic silanes can act as reducing equivalents in an enzyme-catalysed process and that monomeric hydrides of electropositive metals, which are typically unstable in protic environments, can be catalytic intermediates in enzymatic processes. Overall, this work bridges a gap between the types of transformation in molecular catalysis and biocatalysis.
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http://dx.doi.org/10.1038/s41557-020-00633-7DOI Listing
April 2021

Measurements of formation cross-sections of short-lived nuclei around the 14 MeV neutron induced reactions on Hf and Zr and theoretical calculation of excitation functions.

Appl Radiat Isot 2021 Apr 23;170:109588. Epub 2021 Jan 23.

School of Electrical and Mechanical Engineering, Pingdingshan University, Pingdingshan, 467000, China.

The cross sections of the Hf(n,p)Lu and Zr(n,2n)Zr reactions were measured around the neutron energies of 13.5-14.8 MeV by using the activation technique. The excitation functions of the above reactions in the neutron energies from the threshold to 20 MeV were calculated by using the nuclear theoretical model program system Talys-1.9 with the adjusted relevant parameters. The measured results were discussed and compared with previous experiments by other researchers and with the evaluated data of ENDF/B-VIII.0, CENDL-3.1, JEFF-3.3, JENDL-4.0u2, BROND-3.1 as well as the theoretical values based on Talys-1.9. The obtained experimental values at some neutron energies, within experimental error, are consistent with those of the fitting line of the results of previous experiments and are also consistent with those of theoretical excitation curve at the corresponding energies. The obtained theoretical excitation curves match well with most of the experimental data.
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http://dx.doi.org/10.1016/j.apradiso.2021.109588DOI Listing
April 2021

Selenium Nanoparticles Pre-Treatment Reverse Behavioral, Oxidative Damage, Neuronal Loss and Neurochemical Alterations in Pentylenetetrazole-Induced Epileptic Seizures in Mice.

Int J Nanomedicine 2020 24;15:6339-6353. Epub 2020 Aug 24.

Department of Zoology and Entomology, Faculty of Science, Helwan University, Helwan 11795, Egypt.

Introduction: Epilepsy is a chronic neurological condition characterized by behavioral, molecular, and neurochemical alterations. Current antiepileptic drugs are associated with various adverse impacts. The main goal of the current study is to investigate the possible anticonvulsant effect of selenium nanoparticles (SeNPs) against pentylenetetrazole (PTZ)-mediated epileptic seizures in mice hippocampus. Sodium valproate (VPA) was used as a standard anti-epileptic drug.

Methods: Mice were assigned into five groups (n=15): control, SeNPs (5 mg/kg, orally), PTZ (60 mg/kg, intraperitoneally), SeNPs+PTZ and VPA (200 mg/kg)+PTZ. All groups were treated for 10 days.

Results: PTZ injection triggered a state of oxidative stress in the hippocampal tissue as represented by the elevated lipoperoxidation, heat shock protein 70 level, and nitric oxide formation while decreased glutathione level and antioxidant enzymes activity. Additionally, the blotting analysis showed downregulation of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) in the epileptic mice. A state of neuroinflammation was recorded following the developed seizures represented by the increased pro-inflammatory cytokines. Moreover, neuronal apoptosis was recorded following the development of epileptic convulsions. At the neurochemical level, acetylcholinesterase activity and monoamines content were decreased in the epileptic mice, accompanied by high glutamate and low GABA levels in the hippocampal tissue. However, SeNP supplementation was found to delay the onset and decreased the duration of tonic, myoclonic, and generalized seizures following PTZ injection. Moreover, SeNPs were found to provide neuroprotection through preventing the development of oxidative challenge via the upregulation of Nrf2 and HO-1, inhibiting the inflammatory response and apoptotic cascade. Additionally, SeNPs reversed the changes in the activity and levels of neuromodulators following the development of epileptic seizures.

Conclusion: The obtained results suggest that SeNPs could be used as a promising anticonvulsant drug due to its potent antioxidant, anti-inflammatory, and neuromodulatory activities.
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http://dx.doi.org/10.2147/IJN.S259134DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7455605PMC
October 2020

Interference femtosecond laser stamping of micro-grating structures and time-resolved observation of its dynamics.

Opt Express 2020 Jun;28(12):18376-18386

Selective slicing on a 100 nm thick ZnO film deposited on a Si substrate is achieved by an interference femtosecond (fs) laser stamping. A micro-grating structure with a period of ∼5 µm is completely ablated by an energy-optimized single pulse in one step. The elemental mappings demonstrate complete slice removals of the irradiated areas from the substrate without impurities mixed into the thin film. A calculation of the energy transmitted to the substrate and the characterization of the ablated Si channels infer that the irradiated slices are detached from the substrate by the selective ablation of the thin film and the counterforce of the Si substrate. The temporal and spatial evolution of the grating formation is investigated through a pump-probe microscope using the white light continuum (WLC) as the illumination probe. It is found that the extinctive constructive fringes occur at a delay of 8 picosecond (ps) caused by the increase of electron density. The irradiated slices initially bulge at the delay of 10-12 ps, then subsequently swell until strong material ejections at 800 ps. This study provides an opportunity to advance the understanding of micro-grating fabrications and thin film removals on heterostructures using fs lasers.
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http://dx.doi.org/10.1364/OE.390012DOI Listing
June 2020

Multifunctional 3D Micro-Nanostructures Fabricated through Temporally Shaped Femtosecond Laser Processing for Preventing Thrombosis and Bacterial Infection.

ACS Appl Mater Interfaces 2020 Apr 7;12(15):17155-17166. Epub 2020 Feb 7.

Department of Mechanical Engineering, University of Minnesota, 111 Church Street SE, Minneapolis, Minnesota 55455, United States.

Blood-contacting medical devices that directly inhibit thrombosis and bacterial infection without using dangerous anticoagulant and antibacterial drugs can save countless lives but have proved extremely challenging. Here, a useful methodology is proposed that employs temporally shaped femtosecond laser ablation combined with fluorination to fabricate multifunctional three-dimensional (3D) micro-nanostructures with excellent hemocompatibility, zero cytotoxicity, outstanding biocompatibility, bacterial infection prevention, and long-term effectiveness on NiTi alloys. These multifunctional 3D micro-nanostructures present 0.1% hemolysis ratio and almost no platelet adhesion and activation, repel blood to inhibit blood coagulation in vitro, maintain 100% cell viability, and have exceptional stability over 6 months. Moreover, the multifunctional 3D micro-nanostructures simultaneously suppress bacterial colonization to form biofilm and kill 100% colonized () and 95.6% colonized () after 24 h of incubation, and bacterial residues can be easily removed. The fabrication method in this work has the advantages of simple processing, high efficiency, high quality, and high repeatability, and the new multifunctional 3D micro-nanostructures can effectively prevent thrombosis and bacterial infection, which can be widely applied to various clinical needs such as biomedical devices and implants.
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http://dx.doi.org/10.1021/acsami.9b20766DOI Listing
April 2020

Strongly Lewis Acidic Metal-Organic Frameworks for Continuous Flow Catalysis.

J Am Chem Soc 2019 Sep 4;141(37):14878-14888. Epub 2019 Sep 4.

Department of Chemistry , The University of Chicago , 929 East 57th Street , Chicago , Illinois 60637 , United States.

The synthesis of highly acidic metal-organic frameworks (MOFs) has attracted significant research interest in recent years. We report here the design of a strongly Lewis acidic MOF, ZrOTf-BTC, through two-step transformation of MOF-808 (Zr-BTC) secondary building units (SBUs). Zr-BTC was first treated with 1 M hydrochloric acid solution to afford ZrOH-BTC by replacing each bridging formate group with a pair of hydroxide and water groups. The resultant ZrOH-BTC was further treated with trimethylsilyl triflate (MeSiOTf) to afford ZrOTf-BTC by taking advantage of the oxophilicity of the MeSi group. Electron paramagnetic resonance spectra of Zr-bound superoxide and fluorescence spectra of Zr-bound -methylacridone provided a quantitative measurement of Lewis acidity of ZrOTf-BTC with an energy splitting (Δ) of 0.99 eV between the π* and π* orbitals, which is competitive to the homogeneous benchmark Sc(OTf). ZrOTf-BTC was shown to be a highly active solid Lewis acid catalyst for a broad range of important organic transformations under mild conditions, including Diels-Alder reaction, epoxide ring-opening reaction, Friedel-Crafts acylation, and alkene hydroalkoxylation reaction. The MOF catalyst outperformed Sc(OTf) in terms of both catalytic activity and catalyst lifetime. Moreover, we developed a [email protected] composite as an efficient solid Lewis acid catalyst for continuous flow catalysis. The Zr centers in [email protected] feature identical coordination environment to ZrOTf-BTC based on spectroscopic evidence. [email protected] displayed exceptionally high turnover numbers (TONs) of 1700 for Diels-Alder reaction, 2700 for epoxide ring-opening reaction, and 326 for Friedel-Crafts acylation under flow conditions. We have thus created strongly Lewis acidic sites in MOFs via triflation and constructed the [email protected] composite for continuous flow catalysis of important organic transformations.
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http://dx.doi.org/10.1021/jacs.9b07891DOI Listing
September 2019

Structure- and Ligand-Based Discovery of Chromane Arylsulfonamide Na1.7 Inhibitors for the Treatment of Chronic Pain.

J Med Chem 2019 04 16;62(8):4091-4109. Epub 2019 Apr 16.

Xenon Pharmaceuticals, Inc. , 200-3650 Gilmore Way , Burnaby , British Columbia V5G 4W8 , Canada.

Using structure- and ligand-based design principles, a novel series of piperidyl chromane arylsulfonamide Na1.7 inhibitors was discovered. Early optimization focused on improvement of potency through refinement of the low energy ligand conformation and mitigation of high in vivo clearance. An in vitro hepatotoxicity hazard was identified and resolved through optimization of lipophilicity and lipophilic ligand efficiency to arrive at GNE-616 (24), a highly potent, metabolically stable, subtype selective inhibitor of Na1.7. Compound 24 showed a robust PK/PD response in a Na1.7-dependent mouse model, and site-directed mutagenesis was used to identify residues critical for the isoform selectivity profile of 24.
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http://dx.doi.org/10.1021/acs.jmedchem.9b00141DOI Listing
April 2019

N6-Methyladenosine in RNA and DNA: An Epitranscriptomic and Epigenetic Player Implicated in Determination of Stem Cell Fate.

Stem Cells Int 2018 10;2018:3256524. Epub 2018 Oct 10.

Department of Human Genetics, Emory University School of Medicine, 615 Michael St., Atlanta, GA 30322, USA.

Vast emerging evidences are linking the base modifications and determination of stem cell fate such as proliferation and differentiation. Among the base modification markers extensively studied, 5-methylcytosine (5-mC) and its oxidative derivatives (5-hydroxymethylcytosine (5-hmC), 5-formylcytosine (5-fC), and 5-carboxylcytosine (5-caC)) dynamically occur in DNA and RNA and have been acknowledged as important epigenetic markers involved in regulation of cellular biological processes. N6-Methyladenosine modification in DNA (m6dA), mRNA (m6A), tRNA, and other noncoding RNAs has been defined as another important epigenetic and epitranscriptomic marker in eukaryotes in recent years. The mRNA m6A modification has been characterized biochemically, molecularly, and phenotypically, including elucidation of its methyltransferase complexes (m6A writer), demethylases (m6A eraser), and direct interaction proteins (readers), while limited information on the DNA m6dA is available. The levels and the landscapes of m6A in the epitranscriptomes and epigenomes are precisely and dynamically regulated by the fine-tuned coordination of the writers and erasers in accordance with stages of the growth, development, and reproduction as naturally programmed during the lifespan. Additionally, progress has been made in appreciation of the link between aberrant m6A modification in stem cells and diseases, like cancers and neurodegenerative disorders. These achievements are inspiring scientists to further uncover the epigenetic mechanisms for stem cell development and to dissect pathogenesis of the multiple diseases conferred by development aberration of the stem cells. This review article will highlight the research advances in the role of m6A methylation modifications of DNA and RNA in the regulation of stem cell and genesis of the closely related disorders. Additionally, this article will also address the research directions in the future.
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http://dx.doi.org/10.1155/2018/3256524DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6199872PMC
October 2018

Site Isolation in Metal-Organic Frameworks Enables Novel Transition Metal Catalysis.

Acc Chem Res 2018 09 21;51(9):2129-2138. Epub 2018 Aug 21.

Department of Chemistry , The University of Chicago , 929 East 57th Street , Chicago , Illinois 60637 , United States.

Comprising periodically repeating inorganic nodes and organic linkers, metal-organic frameworks (MOFs) represent a novel class of porous molecular solids with well-defined pores and channels. Over the past two decades, a large array of organic linkers have been combined with many inorganic nodes to afford a vast library of MOFs. The synthetic tunability of MOFs distinguishes them from traditional porous inorganic materials and has allowed the rational design of many interesting properties, such as porosity, chirality, and chemical functionality, for potential applications in diverse areas including gas storage and separation, catalysis, light harvesting, chiral separation, and chemical sensing. In particular, the molecular functionality and intrinsic porosity of MOFs have rendered them attractive candidates as porous single-site solid catalysts for a large number of organic transformations. MOF catalysts offer several advantages over their homogeneous counterparts, including enhanced stability, recyclability and reusability, and facile removal of the toxic catalyst components from the organic products. Additionally, the highly ordered nature of MOFs leads to the generation of single-site solid catalysts, allowing for precise characterization of the catalytic sites through X-ray diffraction, X-ray absorption, and other spectroscopic interrogations and facilitating the elucidation of reaction mechanisms. Thus, MOF catalysis represents a fertile research area that is expected to witness continued growth in the foreseeable future. In this Account, we present our recent research progress in developing ligand-supported single-site MOF catalysts for challenging organic reactions. We present two complementary approaches to the design of ligand-supported MOF catalysts: direct incorporation of prefunctionalized organic linkers into MOFs and postsynthetic functionalization of orthogonal secondary functional groups of the organic linkers in MOFs. Monophosphine-, bipyridine-, β-diketimine-, and salicylaldimine-based ligands have been used to support both precious (Pd, Pt, Ir, Ru) and earth-abundant (Cu, Co, Fe) metals for a number of interesting catalytic reactions. The resulting MOF catalysts feature stable low-coordination species with minimum steric bulk around the active site-a feat that remains a challenge for homogeneous catalysts. For each ligand, we describe types of reactions catalyzed by the MOF in comparison with its homogeneous counterpart. In all cases, MOF catalysts outperformed their homogeneous counterparts in terms of catalyst stability, catalytic activity, and recyclability and reusability. Interestingly, several bipyridine- and salicylaldimine-ligated earth-abundant-metal-based MOF catalysts do not have homogeneous counterparts because the molecular compounds disproportionate or oligomerize to form inactive species in solution. This Account not only presents several interesting designs of ligand-supported single-site MOF catalysts but also provides illustrative examples of how site isolation in MOF catalysts shuts down deactivation pathways experienced by homogeneous systems. With precise knowledge of MOF structures and catalytically active sites, we envision the development of practically useful MOF catalysts comprising tailor-made building blocks that rationally optimize catalytic activities and selectivities.
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http://dx.doi.org/10.1021/acs.accounts.8b00297DOI Listing
September 2018

Tuning Lewis Acidity of Metal-Organic Frameworks via Perfluorination of Bridging Ligands: Spectroscopic, Theoretical, and Catalytic Studies.

J Am Chem Soc 2018 08 10;140(33):10553-10561. Epub 2018 Aug 10.

Department of Chemistry , The University of Chicago , 929 East 57th Street , Chicago , Illinois 60637 , United States.

The Lewis acidity of metal-organic frameworks (MOFs) has attracted much research interest in recent years. We report here the development of two quantitative methods for determining the Lewis acidity of MOFs-based on electron paramagnetic resonance (EPR) spectroscopy of MOF-bound superoxide (O) and fluorescence spectroscopy of MOF-bound N-methylacridone (NMA)-and a simple strategy that significantly enhances MOF Lewis acidity through ligand perfluorination. Two new perfluorinated MOFs, Zr-fBDC and Zr-fBPDC, where HfBDC is 2,3,5,6-tetrafluoro-1,4-benzenedicarboxylic acid and HfBPDC is 2,2',3,3',5,5',6,6'-octafluoro-4,4'-biphenyldicarboxylic acid, were shown to be significantly more Lewis acidic than nonsubstituted UiO-66 and UiO-67 as well as the nitrated MOFs Zr-BDC-NO and Zr-BPDC-(NO). Zr-fBDC was shown to be a highly active single-site solid Lewis acid catalyst for Diels-Alder and arene C-H iodination reactions. Thus, this work establishes the important role of ligand perfluorination in enhancing MOF Lewis acidity and the potential of designing highly Lewis acidic MOFs for fine chemical synthesis.
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http://dx.doi.org/10.1021/jacs.8b05765DOI Listing
August 2018

Atomistic insights into the exothermic self-sustained alloying of Al-shell/Ni-core nanoparticle triggered by laser irradiation.

Phys Chem Chem Phys 2018 Aug;20(31):20398-20405

Shenzhen Key Laboratory for Additive Manufacturing of High-Performance Materials, Department of Mechanical and Energy Engineering, Southern University of Science and Technology, Shenzhen 518055, China.

By imposing a picosecond laser pulse irradiation on an Al-shell/Ni-core nanoparticle, an exothermic self-sustained alloying is triggered. Molecular dynamics simulation is implemented to get atomistic insights into the alloying process. The nanoparticle is composed by an equiatomic number of Al atoms in the shell and Ni atoms in the core. Due to the absorption of laser energy from the surface of the nanoparticle, atomic motion becomes active. The inter-diffusion of Ni and Al atoms results in thermal energy generation. It is found that the incident laser energy is responsible for controlling the degree of self-heating of the nanoparticle by governing the potential energy change during the inter-diffusion of Al-shell and Ni-core atoms.
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http://dx.doi.org/10.1039/c8cp03017kDOI Listing
August 2018

Metal-organic layers stabilize earth-abundant metal-terpyridine diradical complexes for catalytic C-H activation.

Chem Sci 2018 Jan 30;9(1):143-151. Epub 2017 Oct 30.

Department of Chemistry , University of Chicago , 929 E. 57th St. , Chicago , Illinois 60637 , USA . Email:

We report the synthesis of a terpyridine-based metal-organic layer (TPY-MOL) and its metalation with CoCl and FeBr to afford CoCl·TPY-MOL and FeBr·TPY-MOL, respectively. Upon activation with NaEtBH, CoCl·TPY-MOL catalyzed benzylic C-H borylation of methylarenes whereas FeBr·TPY-MOL catalyzed intramolecular C -H amination of alkyl azides to afford pyrrolidines and piperidines. X-ray absorption near edge structure (XANES), extended X-ray absorption fine structure (EXAFS), X-ray photoelectron spectroscopy, UV-Vis-NIR spectroscopy, and electron paramagnetic spectroscopy (EPR) measurements as well as density functional theory (DFT) calculations identified M(THF)·TPY-MOL (M = Co or Fe) as the active catalyst with a M-(TPY˙˙) electronic structure featuring divalent metals and TPY diradical dianions. We believe that site isolation stabilizes novel M-(TPY˙˙) (M = Co or Fe) species in the MOLs to endow them with unique and enhanced catalytic activities for C -H borylation and intramolecular amination over their homogeneous counterparts. The MOL catalysts are also superior to their metal-organic framework analogs owing to the removal of diffusion barriers. Our work highlights the potential of MOLs as a novel 2D molecular material platform for designing single-site solid catalysts without diffusional constraints.
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http://dx.doi.org/10.1039/c7sc03537cDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5869321PMC
January 2018

Titanium(III)-Oxo Clusters in a Metal-Organic Framework Support Single-Site Co(II)-Hydride Catalysts for Arene Hydrogenation.

J Am Chem Soc 2018 01 19;140(1):433-440. Epub 2017 Dec 19.

Department of Chemistry, University of Chicago , 929 E. 57th Street, Chicago, Illinois 60637, United States.

Titania (TiO) is widely used in the chemical industry as an efficacious catalyst support, benefiting from its unique strong metal-support interaction. Many proposals have been made to rationalize this effect at the macroscopic level, yet the underlying molecular mechanism is not understood due to the presence of multiple catalytic species on the TiO surface. This challenge can be addressed with metal-organic frameworks (MOFs) featuring well-defined metal oxo/hydroxo clusters for supporting single-site catalysts. Herein we report that the Ti(μ-O)(μ-OH) node of the Ti-BDC MOF (MIL-125) provides a single-site model of the classical TiO support to enable Co-hydride-catalyzed arene hydrogenation. The catalytic activity of the supported Co-hydride is strongly dependent on the reduction of the Ti-oxo cluster, definitively proving the pivotal role of Ti in the performance of the supported catalyst. This work thus provides a molecularly precise model of Ti-oxo clusters for understating the strong metal-support interaction of TiO-supported heterogeneous catalysts.
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http://dx.doi.org/10.1021/jacs.7b11241DOI Listing
January 2018

Trivalent Zirconium and Hafnium Metal-Organic Frameworks for Catalytic 1,4-Dearomative Additions of Pyridines and Quinolines.

J Am Chem Soc 2017 11 25;139(44):15600-15603. Epub 2017 Oct 25.

Department of Chemistry, The University of Chicago , 929 E 57th Street, Chicago, Illinois 60637, United States.

We report the quantitative conversion of [M(μ-O)(μ-OH)Cl] nodes in the MCl-BTC metal-organic framework into the [M(μ-O)(μ-ONa)H] nodes in MH-BTC (M = Zr, Hf; BTC is 1,3,5-benzenetricarboxylate) via bimetallic reductive elimination of H from putative [M(μ-O)(μ-OH)H] nodes. The coordinatively unsaturated MH centers in MH-BTC are highly active and selective for 1,4-dearomative hydroboration and hydrosilylation of pyridines and quinolines. This work demonstrated the potential of secondary building unit transformation in generating electronically unique and homogeneously inaccessible single-site solid catalysts for organic synthesis.
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http://dx.doi.org/10.1021/jacs.7b09093DOI Listing
November 2017

Transformation of Metal-Organic Framework Secondary Building Units into Hexanuclear Zr-Alkyl Catalysts for Ethylene Polymerization.

J Am Chem Soc 2017 08 15;139(33):11325-11328. Epub 2017 Aug 15.

Department of Chemistry, The University of Chicago , 929 E 57th Street, Chicago, Illinois 60637, United States.

We report the stepwise and quantitative transformation of the Zr(μ-O)(μ-OH)(HCO) nodes in Zr-BTC (MOF-808) to the [Zr(μ-O)(μ-OH)Cl] nodes in ZrCl-BTC, and then to the organometallic [Zr(μ-O)(μ-OLi)R] nodes in ZrR-BTC (R = CHSiMe or Me). Activation of ZrCl-BTC with MMAO-12 generates ZrMe-BTC, which is an efficient catalyst for ethylene polymerization. ZrMe-BTC displays unusual electronic and steric properties compared to homogeneous Zr catalysts, possesses multimetallic active sites, and produces high-molecular-weight linear polyethylene. Metal-organic framework nodes can thus be directly transformed into novel single-site solid organometallic catalysts without homogeneous analogs for polymerization reactions.
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http://dx.doi.org/10.1021/jacs.7b05761DOI Listing
August 2017

Electron Crystallography Reveals Atomic Structures of Metal-Organic Nanoplates with M(μ-O)(μ-OH)(μ-OH) (M = Zr, Hf) Secondary Building Units.

Inorg Chem 2017 Jul 22;56(14):8128-8134. Epub 2017 Jun 22.

College of Chemistry and Chemical Engineering, iCHEM, PCOSS, Xiamen University , Xiamen 361005, People's Republic of China.

Nanoscale metal-organic frameworks (nMOFs) have shown tremendous potential in cancer therapy and biomedical imaging. However, their small dimensions present a significant challenge in structure determination by single-crystal X-ray crystallography. We report here the structural determination of nMOFs by rotation electron diffraction (RED). Two isostructural Zr- and Hf-based nMOFs with linear biphenyldicarboxylate (BPDC) or bipyridinedicarboxylate (BPYDC) linkers are stable under intense electron beams to allow the collection of high-quality RED data, which reveal a MOF structure with M(μ-O)(μ-OH)(μ-OH) (M = Zr, Hf) secondary building units (SBUs). The nMOF structures differ significantly from their UiO bulk counterparts with M(μ-O)(μ-OH) SBUs and provide the foundation for clarifying the structures of a series of previously reported nMOFs with significant potential in cancer therapy and biological imaging. Our work clearly demonstrates the power of RED in determining nMOF structures and elucidating the formation mechanism of distinct nMOF morphologies.
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http://dx.doi.org/10.1021/acs.inorgchem.7b00845DOI Listing
July 2017

Phenanthroline-based metal-organic frameworks for Fe-catalyzed C-H amination.

Faraday Discuss 2017 09;201:303-315

Department of Chemistry, University of Chicago, 929 East 57th, Street, Chicago, Illinois 60637, USA.

We report here the synthesis of a robust and highly porous Fe-phenanthroline-based metal-organic framework (MOF) and its application in catalyzing challenging inter- and intramolecular C-H amination reactions. For the intermolecular amination reactions, a FeBr-metalated MOF selectively functionalized secondary benzylic and allylic C-H bonds. The intramolecular amination reactions utilizing organic azides as the nitrene source required the reduction of the FeBr-metalated MOF with NaBHEt to generate the active catalyst. For both reactions, Fe or Zr leaching was less than 0.1%, and MOFs could be recycled and reused with no loss in catalytic activity. Furthermore, MOF catalysts were significantly more active than the corresponding homogeneous analogs. This work demonstrates the great potential of MOFs in generating highly active, recyclable, and reusable earth abundant metal catalysts for challenging organic transformations.
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http://dx.doi.org/10.1039/c7fd00030hDOI Listing
September 2017

Single-Site Cobalt Catalysts at New Zr(μ-O)(μ-OH)(μ-OH) Metal-Organic Framework Nodes for Highly Active Hydrogenation of Nitroarenes, Nitriles, and Isocyanides.

J Am Chem Soc 2017 05 11;139(20):7004-7011. Epub 2017 May 11.

Department of Chemistry, University of Chicago , 929 East 57th Street, Chicago, Illinois 60637, United States.

We report here the synthesis of a robust and porous metal-organic framework (MOF), Zr-TPDC, constructed from triphenyldicarboxylic acid (HTPDC) and an unprecedented Zr secondary building unit (SBU): Zr(μ-O)(μ-OH)(μ-OH). The Zr-SBU can be viewed as an inorganic node dimerized from two commonly observed Zr clusters via six μ-OH groups. The metalation of Zr-TPDC SBUs with CoCl followed by treatment with NaBEtH afforded a highly active and reusable solid Zr-TPDC-Co catalyst for the hydrogenation of nitroarenes, nitriles, and isocyanides to corresponding amines with excellent activity and selectivity. This work highlights the opportunity in designing novel MOF-supported single-site solid catalysts by tuning the electronic and steric properties of the SBUs.
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http://dx.doi.org/10.1021/jacs.7b02394DOI Listing
May 2017

Confinement of Ultrasmall Cu/ZnO Nanoparticles in Metal-Organic Frameworks for Selective Methanol Synthesis from Catalytic Hydrogenation of CO.

J Am Chem Soc 2017 03 2;139(10):3834-3840. Epub 2017 Mar 2.

Collaborative Innovation Center of Chemistry for Energy Materials, State Key Laboratory of Physical Chemistry of Solid Surfaces, Department of Chemistry, College of Chemistry and Chemical Engineering, Xiamen University , Xiamen 361005, PR China.

The interfaces of Cu/ZnO and Cu/ZrO play vital roles in the hydrogenation of CO to methanol by these composite catalysts. Surface structural reorganization and particle growth during catalysis deleteriously reduce these active interfaces, diminishing both catalytic activities and MeOH selectivities. Here we report the use of preassembled bpy and Zr(μ-O)(μ-OH) sites in UiO-bpy metal-organic frameworks (MOFs) to anchor ultrasmall Cu/ZnO nanoparticles, thus preventing the agglomeration of Cu NPs and phase separation between Cu and ZnO in MOF-cavity-confined Cu/ZnO nanoparticles. The resultant Cu/[email protected] catalysts show very high activity with a space-time yield of up to 2.59 g kg h, 100% selectivity for CO hydrogenation to methanol, and high stability over 100 h. These new types of strong metal-support interactions between metallic nanoparticles and organic chelates/metal-oxo clusters offer new opportunities in fine-tuning catalytic activities and selectivities of metal [email protected]
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http://dx.doi.org/10.1021/jacs.7b00058DOI Listing
March 2017

Cerium-Hydride Secondary Building Units in a Porous Metal-Organic Framework for Catalytic Hydroboration and Hydrophosphination.

J Am Chem Soc 2016 11 4;138(45):14860-14863. Epub 2016 Nov 4.

Department of Chemistry, University of Chicago , 929 East 57th Street, Chicago, Illinois 60637, United States.

We report the stepwise, quantitative transformation of Ce(μ-O)(μ-OH)(OH)(OH) nodes in a new Ce-BTC (BTC = trimesic acid) metal-organic framework (MOF) into the first Ce(μ-O)(μ-OLi)(H)(THF)Li metal-hydride nodes that effectively catalyze hydroboration and hydrophosphination reactions. CeH-BTC displays low steric hindrance and electron density compared to homogeneous organolanthanide catalysts, which likely accounts for the unique 1,4-regioselectivity for the hydroboration of pyridine derivatives. MOF nodes can thus be directly transformed into novel single-site solid catalysts without homogeneous counterparts for sustainable chemical synthesis.
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http://dx.doi.org/10.1021/jacs.6b10055DOI Listing
November 2016

Single-Site Cobalt Catalysts at New Zr8(μ2-O)8(μ2-OH)4 Metal-Organic Framework Nodes for Highly Active Hydrogenation of Alkenes, Imines, Carbonyls, and Heterocycles.

J Am Chem Soc 2016 09 6;138(37):12234-42. Epub 2016 Sep 6.

Department of Chemistry, University of Chicago , 929 E. 57th St., Chicago, Illinois 60637, United States.

We report here the synthesis of robust and porous metal-organic frameworks (MOFs), M-MTBC (M = Zr or Hf), constructed from the tetrahedral linker methane-tetrakis(p-biphenylcarboxylate) (MTBC) and two types of secondary building units (SBUs): cubic M8(μ2-O)8(μ2-OH)4 and octahedral M6(μ3-O)4(μ3-OH)4. While the M6-SBU is isostructural with the 12-connected octahedral SBUs of UiO-type MOFs, the M8-SBU is composed of eight M(IV) ions in a cubic fashion linked by eight μ2-oxo and four μ2-OH groups. The metalation of Zr-MTBC SBUs with CoCl2, followed by treatment with NaBEt3H, afforded highly active and reusable solid Zr-MTBC-CoH catalysts for the hydrogenation of alkenes, imines, carbonyls, and heterocycles. Zr-MTBC-CoH was impressively tolerant of a range of functional groups and displayed high activity in the hydrogenation of tri- and tetra-substituted alkenes with TON > 8000 for the hydrogenation of 2,3-dimethyl-2-butene. Our structural and spectroscopic studies show that site isolation of and open environments around the cobalt-hydride catalytic species at Zr8-SBUs are responsible for high catalytic activity in the hydrogenation of a wide range of challenging substrates. MOFs thus provide a novel platform for discovering and studying new single-site base-metal solid catalysts with enormous potential for sustainable chemical synthesis.
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http://dx.doi.org/10.1021/jacs.6b06759DOI Listing
September 2016

Chemoselective single-site Earth-abundant metal catalysts at metal-organic framework nodes.

Nat Commun 2016 08 30;7:12610. Epub 2016 Aug 30.

Department of Chemistry, The University of Chicago, 929 E 57th Street, Chicago, Illinois 60637, USA.

Earth-abundant metal catalysts are critically needed for sustainable chemical synthesis. Here we report a simple, cheap and effective strategy of producing novel earth-abundant metal catalysts at metal-organic framework (MOF) nodes for broad-scope organic transformations. The straightforward metalation of MOF secondary building units (SBUs) with cobalt and iron salts affords highly active and reusable single-site solid catalysts for a range of organic reactions, including chemoselective borylation, silylation and amination of benzylic C-H bonds, as well as hydrogenation and hydroboration of alkenes and ketones. Our structural, spectroscopic and kinetic studies suggest that chemoselective organic transformations occur on site-isolated, electron-deficient and coordinatively unsaturated metal centres at the SBUs via σ-bond metathesis pathways and as a result of the steric environment around the catalytic site. MOFs thus provide a novel platform for the development of highly active and affordable base metal catalysts for the sustainable synthesis of fine chemicals.
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http://dx.doi.org/10.1038/ncomms12610DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5013626PMC
August 2016

Metal-Organic Framework Nodes Support Single-Site Magnesium-Alkyl Catalysts for Hydroboration and Hydroamination Reactions.

J Am Chem Soc 2016 06 10;138(24):7488-91. Epub 2016 Jun 10.

Department of Chemistry, University of Chicago , 929 East 57th Street, Chicago, Illinois 60637, United States.

Here we present the first example of a single-site main group catalyst stabilized by a metal-organic framework (MOF) for organic transformations. The straightforward metalation of the secondary building units of a Zr-MOF with Me2Mg affords a highly active and reusable solid catalyst for hydroboration of carbonyls and imines and for hydroamination of aminopentenes. Impressively, the Mg-functionalized MOF displayed very high turnover numbers of up to 8.4 × 10(4) for ketone hydroboration and could be reused more than 10 times. MOFs can thus be used to develop novel main group solid catalysts for sustainable chemical synthesis.
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http://dx.doi.org/10.1021/jacs.6b03689DOI Listing
June 2016

Induced Pluripotent Stem Cells: Generation Strategy and Epigenetic Mystery behind Reprogramming.

Stem Cells Int 2016 5;2016:8415010. Epub 2016 Jan 5.

Department of Human Genetics, Emory University School of Medicine, 615 Michael Street, Atlanta, GA 30322, USA.

Possessing the ability of self-renewal with immortalization and potential for differentiation into different cell types, stem cells, particularly embryonic stem cells (ESC), have attracted significant attention since their discovery. As ESC research has played an essential role in developing our understanding of the mechanisms underlying reproduction, development, and cell (de)differentiation, significant efforts have been made in the biomedical study of ESC in recent decades. However, such studies of ESC have been hampered by the ethical issues and technological challenges surrounding them, therefore dramatically inhibiting the potential applications of ESC in basic biomedical studies and clinical medicine. Induced pluripotent stem cells (iPSCs), generated from the reprogrammed somatic cells, share similar characteristics including but not limited to the morphology and growth of ESC, self-renewal, and potential differentiation into various cell types. The discovery of the iPSC, unhindered by the aforementioned limitations of ESC, introduces a viable alternative to ESC. More importantly, the applications of iPSC in the development of disease models such as neurodegenerative disorders greatly enhance our understanding of the pathogenesis of such diseases and also facilitate the development of clinical therapeutic strategies using iPSC generated from patient somatic cells to avoid an immune rejection. In this review, we highlight the advances in iPSCs generation methods as well as the mechanisms behind their reprogramming. We also discuss future perspectives for the development of iPSC generation methods with higher efficiency and safety.
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http://dx.doi.org/10.1155/2016/8415010DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4736417PMC
February 2016

The first chiral diene-based metal-organic frameworks for highly enantioselective carbon-carbon bond formation reactions.

Chem Sci 2015 Dec 14;6(12):7163-7168. Epub 2015 Sep 14.

Department of Chemistry , University of Chicago , 929 E 57th St , Chicago , Illinois 60637 , USA . Email:

We have designed the first chiral diene-based metal-organic framework (MOF), E-MOF, and postsynthetically metalated E-MOF with Rh(i) complexes to afford highly active and enantioselective single-site solid catalysts for C-C bond formation reactions. Treatment of E-MOF with [RhCl(CH)] led to a highly enantioselective catalyst for 1,4-additions of arylboronic acids to α,β-unsaturated ketones, whereas treatment of E-MOF with Rh(acac)(CH) afforded a highly efficient catalyst for the asymmetric 1,2-additions of arylboronic acids to aldimines. Interestingly, E-MOF·Rh(acac) showed higher activity and enantioselectivity than the homogeneous control catalyst, likely due to the formation of a true single-site catalyst in the MOF. E-MOF·Rh(acac) was also successfully recycled and reused at least seven times without loss of yield and enantioselectivity.
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http://dx.doi.org/10.1039/c5sc02100fDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5951194PMC
December 2015

Palladium-catalyzed decarboxylative generation and asymmetric allylation of α-imino anions.

Org Lett 2014 Oct 22;16(19):5228-31. Epub 2014 Sep 22.

Key Laboratory of Green Chemistry & Technology, College of Chemistry, Sichuan University , Chengdu, Sichuan 610064, P. R. China.

A palladium-catalyzed asymmetric decarboxylative allylic alkylation of allyl 2,2-diphenylglycinate imines using (S,S)-f-binaphane as a chiral supporting ligand has been developed. This transformation allows for decarboxylative generation and enantioselective allylation of nonenolate α-imino (2-azaallyl anions) to afford α-aryl homoallylic imines.
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http://dx.doi.org/10.1021/ol502693rDOI Listing
October 2014

Simultaneous catalyst-free growth of highly oriented ZnO nanowires and microtubes.

J Nanosci Nanotechnol 2013 Aug;13(8):5919-23

State Key Laboratory of Advanced Metallurgy, Department of Physical Chemistry, University of Science and Technology, Beijing 100083, China.

Through a catalyst-free chemical vapor deposition method, highly oriented ZnO nanowires and microtubes were simultaneously grown on the side and the top surface of Si substrate respectively. The ZnO nanowires and microtubes were characterized by scanning electron microscopy, X-ray diffraction, transmission electron microscopy and selected area electron diffraction. The growth mechanism of the microtubes was discussed and the room temperature photoluminescence properties of individual microtubes were investigated.
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http://dx.doi.org/10.1166/jnn.2013.7519DOI Listing
August 2013
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