Publications by authors named "Mizuho Yabushita"

8 Publications

  • Page 1 of 1

Adsorption of Keggin-Type Polyoxometalates on Rh Metal Particles under Reductive Conditions.

Inorg Chem 2021 Aug 29;60(16):12413-12424. Epub 2021 Jul 29.

Department of Applied Chemistry, School of Engineering, Tohoku University, 6-6-07 Aoba, Aramaki, Aoba-ku, Sendai 980-8579, Japan.

The adsorption of POMs on Rh/SiO in water solvent under strongly reductive conditions was investigated. Aqueous solutions of α-Keggin type silicotungstate and silicovanadotungstates were mixed with Rh/SiO at 393-473 K under 1 MPa of H. Monovanadium-substituted silicotungstate, α-SiVWO (SiVW), was more readily adsorbed than nonsubstituted silicotungstate, α-SiWO (SiW). After adsorption at 433 K, SiVW was desorbed from Rh/SiO by oxidation with Br water without change of the Keggin structure, as evidenced by V NMR. Trivanadium-substituted silicotungstate, α-1,2,3-SiVWO, was not stable, and the desorbed species from Rh/SiO by oxidation with Br did not maintain the Keggin structure. The very high temperature for adsorption (473 K) also led to the decomposition of the Keggin structure of SiVW. An increase in the concentration of SiVW in the liquid phase gave a saturation of the amount of desorbable SiVW, up to five SiVW anions per one Rh particle with a 3 nm size. The elemental analysis and W L-edge extended X-ray absorption fine structure of Rh/SiO after the adsorption of SiVW showed that a part of SiVW was decomposed and irreversibly adsorbed as metallic W species incorporated into the surface of Rh metal particles. The amount of decomposed SiVW was almost the same as that of SiVW adsorbed as the original Keggin structure. The desorbable SiVW was probably bonded on the W atom incorporated on the Rh metal particles as the two-electron-reduced form (α-SiVWO).
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http://dx.doi.org/10.1021/acs.inorgchem.1c01644DOI Listing
August 2021

Organic Structure-Directing Agent-Free Synthesis of Mordenite-Type Zeolites Driven by Al-Rich Amorphous Aluminosilicates.

ACS Omega 2021 Mar 16;6(8):5176-5182. Epub 2021 Feb 16.

Institute of Multidisciplinary Research for Advanced Materials, Tohoku University, 2-1-1 Katahira, Aoba-ku, Sendai, Miyagi 980-8577, Japan.

Mordenite (MOR)-type zeolites with a Si/Al molar ratio of up to 13 with crystallite sizes of ca. 60 nm were successfully synthesized from Al-rich aluminosilicates with a Si/Al ratio of 2 and additional SiO under seed-assisted hydrothermal conditions for 6 h or longer without any organic structure-directing agents (OSDAs). In stark contrast, under the same hydrothermal conditions for 6 h, control experiments using starting reagent(s), such as Al-poor aluminosilicate, pure SiO, tetraethyl orthosilicate, and Al(NO), all of which are typically employed for zeolite synthesis, failed to yield MOR-type zeolites. The penta-coordinated Al species, which are present in Al-rich aluminosilicates and are more reactive than the tetra- and hexa-coordinated Al species typically found in alumina and Al-poor aluminosilicates, played a decisive role in the OSDA-free synthesis of MOR-type zeolites.
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http://dx.doi.org/10.1021/acsomega.0c05059DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7931214PMC
March 2021

Selective Sequestration of Aromatics from Aqueous Mixtures with Sugars by Hydrophobic Molecular Calixarene Cavities Grafted on Silica.

ACS Appl Mater Interfaces 2018 Nov 6;10(46):39670-39678. Epub 2018 Nov 6.

Department of Chemical and Biomolecular Engineering , University of California, Berkeley , Berkeley , California 94720 , United States.

The separation of aromatic contaminants from sugar-aromatic aqueous mixtures is required in second-generation biorefineries because aromatic compounds deactivate (bio)catalysts typically involved in upgrading lignocellulosic biomass to fuels and chemicals. This separation remains challenging, however, because of the degree of molecular recognition needed to sequester dilute aromatic impurities from concentrated sugar streams. Herein, we demonstrate that hydrophobic cavities of p- tert-butylcalix[4]arene macrocycles grafted on amorphous silica (calix/SiO) perform this separation selectively and efficiently by acting as selective molecular hosts that adsorb aromatic compounds (5-hydroxymethylfurfural, vanillin, and vanillic acid) while excluding monomeric sugar (glucose chosen as a prototypical model) in aqueous mixtures. By comparing calix/SiO to a range of organically modified SiO surfaces and other porous adsorbents, we demonstrate that the organization of hydrophobic functional groups within discrete nests consisting of calixarene cavities is crucial for facilitating the adsorption of aromatics. Density functional theory calculations of the host-guest complex indicate that adsorption is brought about by weak dispersive (van der Waals) interactions between tert-butyl upper-rim substituents in calixarene hosts and aromatic guests. Calix/SiO can be repeatedly reused, demonstrating its viability as an adsorbent within a continuous biorefining process. These calix/SiO adsorbents expand the palette of materials available for selective sugar-aromatic separations, which until now have been limited to pyrene-based sites of metal-organic framework NU-1000, and demonstrate that sites consisting of relatively simple hydrophobic tert-butyl substituents organized around a hemispherical molecular cavity provide a sufficient degree of molecular recognition for performing this separation selectively.
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http://dx.doi.org/10.1021/acsami.8b13273DOI Listing
November 2018

Insights into Supramolecular Sites Responsible for Complete Separation of Biomass-Derived Phenolics and Glucose in Metal-Organic Framework NU-1000.

Langmuir 2017 05 19;33(17):4129-4137. Epub 2017 Apr 19.

Department of Chemistry, Northwestern University , Evanston, Illinois 60208, United States.

The molecular origins of adsorption of lignin-derived phenolics to metal-organic framework NU-1000 are investigated from aqueous solution as well as in competitive mode with glucose present in the same aqueous mixture. A comparison of adsorption equilibrium constants (K) for phenolics functionalized with either carboxylic acid or aldehyde substituents demonstrated only a slight increase (less than a factor of 6) for the former according to both experiments and calculations. This small difference in K between aldehyde and carboxylic-acid substituted adsorbates is consistent with the pyrene unit of NU-1000 as the adsorption site, rather than the zirconia nodes, while at saturation coverage, the adsorption capacity suggests multiple guests per pyrene. Experimental standard free energies of adsorption directly correlated with the molecular size and electronic structure calculations confirmed this direct relationship, with the pyrene units as adsorption site. The underlying origins of this relationship are grounded in noncovalent π-π interactions as being responsible for adsorption, the same interactions present in the condensed phase of the phenolics, which to a large extent govern their heat of vaporization. Thus, NU-1000 acts as a preformed aromatic cavity for driving aromatic guest adsorption from aqueous solution and does so specifically without causing detectable glucose adsorption from aqueous solution, thereby achieving complete glucose-phenolics separations. The reusability of NU-1000 during an adsorption/desorption cycle was good, even with some of the phenolic compounds with greatest affinity not easiliy removed with water and ethanol washes at room temperature. A competitive adsorption experiment gave an upper bound for K for glucose of at most 0.18 M, which can be compared with K for the phenolics investigated here, which fell in the range of 443-42 639 M. The actual value of K for glucose may be much closer to zero given the lack of observed glucose uptake with NU-1000 as adsorbent.
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http://dx.doi.org/10.1021/acs.langmuir.7b00045DOI Listing
May 2017

Complete furanics-sugar separations with metal-organic framework NU-1000.

Chem Commun (Camb) 2016 Sep;52(79):11791-11794

Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, USA.

Metal-organic framework NU-1000 selectively adsorbs furanics, while completely excluding the adsorption of monomeric sugars from the same aqueous mixture. The highly refined degree of molecular recognition exhibited by NU-1000 is exemplified with it selectively adsorbing 5-hydroxymethylfurfural, even in the presence of up to a 300-fold excess of glucose in solution.
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http://dx.doi.org/10.1039/c6cc05864gDOI Listing
September 2016

Unprecedented selectivity in molecular recognition of carbohydrates by a metal-organic framework.

Chem Commun (Camb) 2016 06 17;52(44):7094-7. Epub 2016 May 17.

Department of Chemical and Biomolecular Engineering, University of California, Berkeley, California 94720, USA.

Metal-organic framework (MOF) material NU-1000 adsorbs dimers cellobiose and lactose from aqueous solution, in amounts exceeding 1250 mg gNU-1000(-1) while completely excluding the adsorption of the monomer glucose, even in a competitive mode with cellobiose. The MOF also discriminates between dimers consisting of α and β linkages, showing no adsorption of maltose. Electronic structure calculations demonstrate that key to this selective molecular recognition is the number of favorable CH-π interactions made by the sugar with pyrene units of the MOF.
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http://dx.doi.org/10.1039/c6cc03266dDOI Listing
June 2016

Catalytic Depolymerization of Chitin with Retention of N-Acetyl Group.

ChemSusChem 2015 Nov 5;8(22):3760-3. Epub 2015 Nov 5.

Institute for Catalysis, Hokkaido University, Kita 21 Nishi 10, Kita-ku, Sapporo, Hokkaido, 001-0021, Japan.

Chitin, a polymer of N-acetylglucosamine units with β-1,4-glycosidic linkages, is the most abundant marine biomass. Chitin monomers containing N-acetyl groups are useful precursors to various fine chemicals and medicines. However, the selective conversion of robust chitin to N-acetylated monomers currently requires a large excess of acid or a long reaction time, which limits its application. We demonstrate a fast catalytic transformation of chitin to monomers with retention of N-acetyl groups by combining mechanochemistry and homogeneous catalysis. Mechanical-force-assisted depolymerization of chitin with a catalytic amount of H2SO4 gave soluble short-chain oligomers. Subsequent hydrolysis of the ball-milled sample provided N-acetylglucosamine in 53% yield, and methanolysis afforded 1-O-methyl-N-acetylglucosamine in yields of up to 70%. Our process can greatly reduce the use of acid compared to the conventional process.
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http://dx.doi.org/10.1002/cssc.201501224DOI Listing
November 2015

Entropically favored adsorption of cellulosic molecules onto carbon materials through hydrophobic functionalities.

ChemSusChem 2014 May 18;7(5):1443-50. Epub 2014 Mar 18.

Catalysis Research Center, Hokkaido University, Kita 21 Nishi 10, Kita-ku, Sapporo, Hokkaido 001-0021 (Japan); Division of Chemical Sciences and Engineering, Graduate School of Chemical Sciences and Engineering, Hokkaido University, Kita 13 Nishi 8, Kita-ku, Sapporo, Hokkaido 060-8628 (Japan).

Carbon-based materials have attracted interest as high-performance catalysts for the aqueous-phase conversion of cellulose. The adsorption of β-glucans plays a crucial role in the catalytic performance of carbons, although the primary driving force and details of the adsorption process remain unclear. This study demonstrates that adsorption occurs at hydrophobic sites on the carbon surface and that hydrophilic groups are not involved. Analysis of adsorption temperature dependence also reveals that the entropy change associated with adsorption is positive. Our results indicate that adsorption occurs by entropically driven hydrophobic interactions in addition to CH-π hydrogen bonding. These same CH-π hydrogen bonds are also confirmed by DFT calculations. The adsorption of β-glucans on carbons is significantly stronger than the affinity between β-glucans. The adsorption equilibrium constants of β-glucans on carbons increase exponentially with increasing degrees of polymerization, which supports the theory of strong interactions between the carbon and the long β-glucans found in cellulose.
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http://dx.doi.org/10.1002/cssc.201301296DOI Listing
May 2014
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