Controlling Reduction Potentials of Semiconductor-Supported Molecular Catalysts for Environmental Remediation of Organohalide Pollutants

2005 ◽  
Vol 39 (16) ◽  
pp. 6266-6272 ◽  
Author(s):  
Sherine O. Obare ◽  
Tamae Ito ◽  
Gerald J. Meyer
Keyword(s):  
Environmental Remediation ◽  
Reduction Potentials ◽  
Molecular Catalysts

Crystal structures of hybrid completely reduced phosphomolybdates and catalytic performance applied as molecular catalysts for the reduction of chromium(VI)

2018 ◽  
Vol 74 (11) ◽  
pp. 1310-1324 ◽  
Author(s):  
Xuerui Tian ◽  
Xing Xin ◽  
Yuanzhe Gao ◽  
Dandan Dai ◽  
Jinjin Huang ◽  
...  
Keyword(s):  
Environmental Remediation ◽  
Catalytic Reduction ◽  
Noncovalent Interactions ◽  
Low Cost ◽  
Catalytic Performance ◽  
Vital Role ◽  
Chromium Vi ◽  
Highly Active ◽  
Supramolecular Networks ◽  
Molecular Catalysts

The exploration of highly efficient and low-cost catalysts for the treatment of hexavalent chromium CrVI in environmental remediation is currently one of the most challenging topics. Here, three phosphomolybdate hybrid compounds have been successfully isolated by the hydrothermal method and been applied as supramolecular catalysts for the reduction of CrVI. Single-crystal X-ray diffraction revealed their formulae as (H2bpp)2[Fe(H2O)][Sr(H2O)4]2{Fe[Mo6O12(OH)3(H2PO4)(HPO4)(PO4)2]2}·5H2O (1), (H2bpp)2[Na(H2O)(OC2H5)][Fe(H2O)2][Ca(H2O)2]2{Fe[Mo6O12(OH)3(H2PO4)(HPO4)(PO4)2]2}·4H2O (2) and (H2bpe)3{Fe[Mo6O12(OH)3(HPO4)3(H2PO4)]2}·8H2O (3) [bpp is 1,3-bis(pyridin-4-yl)propane (C13H14N2) and bpe is trans-1,2-bis(pyridin-4-yl)ethylene (C12H10N2)]. The three hybrids consist of supramolecular networks built up by noncovalent interactions between {Fe[P4Mo6 VO31]2}22− polyanions and protonated organic cations. This kind of hybrid polyoxometalate could be applied as heterogeneous molecular catalysts for the reduction of CrVI. It was found that the organic moiety plays a vital role in influencing the catalytic activity of the polyanions. Organic bpp-containing hybrids 1 and 2 are highly active in the catalytic reduction of heavy metal CrVI ions using HCOOH as reductant, while bpe-containing hybrid 3 is inactive to this reaction. This work is significant for the design of new catalysts, as well as the exploration of reaction mechanisms at a molecular level.

A peek in the micro-sized world: a review of design principles, engineering tools, and applications of engineered microbial community

2020 ◽  
Vol 48 (2) ◽  
pp. 399-409
Author(s):  
Baizhen Gao ◽  
Rushant Sabnis ◽  
Tommaso Costantini ◽  
Robert Jinkerson ◽  
Qing Sun
Keyword(s):  
Microbial Community ◽  
Microbial Communities ◽  
Environmental Remediation ◽  
Real Life ◽  
Design Principles ◽  
Microbial Interactions ◽  
Potential Applications ◽  
New Gene ◽  
Global Biogeochemical Cycles ◽  
Synthetic Microbial Communities

Microbial communities drive diverse processes that impact nearly everything on this planet, from global biogeochemical cycles to human health. Harnessing the power of these microorganisms could provide solutions to many of the challenges that face society. However, naturally occurring microbial communities are not optimized for anthropogenic use. An emerging area of research is focusing on engineering synthetic microbial communities to carry out predefined functions. Microbial community engineers are applying design principles like top-down and bottom-up approaches to create synthetic microbial communities having a myriad of real-life applications in health care, disease prevention, and environmental remediation. Multiple genetic engineering tools and delivery approaches can be used to ‘knock-in' new gene functions into microbial communities. A systematic study of the microbial interactions, community assembling principles, and engineering tools are necessary for us to understand the microbial community and to better utilize them. Continued analysis and effort are required to further the current and potential applications of synthetic microbial communities.

Cobaloxime-Based Double Complex Salts as Efficient and Versatile Catalysts for the Light-Driven Hydrogen Evolution Reaction

2020 ◽  
Author(s):  
Elisabeth Hofmeister ◽  
Jisoo Woo ◽  
Tobias Ullrich ◽  
Lydia Petermann ◽  
Kevin Hanus ◽  
...  
Keyword(s):  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Systematic Study ◽  
Cobalt Complexes ◽  
Spectroscopic Studies ◽  
Double Complex ◽  
Double Complex Salts ◽  
Noble Metal Catalysts ◽  
Reduction Potentials ◽  
Complex Salts

Cobaloximes and their BF<sub>2</sub>-bridged analogues have emerged as promising non-noble metal catalysts for the photocatalytic hydrogen evolution reaction (HER). Herein we report the serendipitous discovery that double complex salts such as [Co(dmgh)<sub>2</sub>py<sub>2</sub>]<sup>+</sup>[Co(dmgBPh<sub>2</sub>)<sub>2</sub>Cl<sub>2</sub>]<sup>-</sup> can be obtained in good yields by treatment of commercially available [Co(dmgh)<sub>2</sub>pyCl] with triarylboranes. A systematic study on the use of such double complex salts and their single salts with simple counterions as photocatalysts revealed HER activities comparable or superior to existing cobaloxime catalysts and suggests ample opportunities for this compound class in catalyst/photosensitizer dyads and immobilized architectures. Preliminary electrochemical and spectroscopic studies indicate that one key advantage of these charged cobalt complexes is that the reduction potentials as well as the electrostatic interaction with charged photosensitizers can be tuned.

An NADH-Inspired Redox Mediator Strategy to Promote Second-Sphere Electron and Proton Transfer for Cooperative Electrochemical CO2 Reduction Catalyzed by Iron Porphyrin

2020 ◽  
Author(s):  
Peter T. Smith ◽  
Sophia Weng ◽  
Christopher Chang
Keyword(s):  
Proton Transfer ◽  
Co2 Reduction ◽  
Iron Porphyrin ◽  
Redox Mediators ◽  
Reservoir Properties ◽  
Proton Reduction ◽  
Electrochemical Co2 Reduction ◽  
Starting Point ◽  
Rate Improvement ◽  
Molecular Catalysts

We present a bioinspired strategy for enhancing electrochemical carbon dioxide reduction catalysis by cooperative use of base-metal molecular catalysts with intermolecular second-sphere redox mediators that facilitate both electron and proton transfer. Functional synthetic mimics of the biological redox cofactor NADH, which are electrochemically stable and are capable of mediating both electron and proton transfer, can enhance the activity of an iron porphyrin catalyst for electrochemical reduction of CO<sub>2</sub> to CO, achieving a 13-fold rate improvement without altering the intrinsic high selectivity of this catalyst platform for CO<sub>2</sub> versus proton reduction. Evaluation of a systematic series of NADH analogs and redox-inactive control additives with varying proton and electron reservoir properties reveals that both electron and proton transfer contribute to the observed catalytic enhancements. This work establishes that second-sphere dual control of electron and proton inventories is a viable design strategy for developing more effective electrocatalysts for CO<sub>2</sub> reduction, providing a starting point for broader applications of this approach to other multi-electron, multi-proton transformations.

Host-Guest Interactions on Electrode Surfaces for Immobilization of Molecular Catalysts

2020 ◽  
Author(s):  
Laurent Sévery ◽  
Jacek Szczerbiński ◽  
Mert Taskin ◽  
Isik Tuncay ◽  
Fernanda Brandalise Nunes ◽  
...  
Keyword(s):  
Aqueous Media ◽  
Heterogeneous Systems ◽  
Catalytic Systems ◽  
New Approach ◽  
Molecular Systems ◽  
Electrode Surfaces ◽  
Catalytic Surfaces ◽  
Oxide Electrodes ◽  
The Stability ◽  
Molecular Catalysts

The strategy of anchoring molecular catalysts on electrode surfaces combines the high selectivity and activity of molecular systems with the practicality of heterogeneous systems. The stability of molecular catalysts is, however, far less than that of traditional heterogeneous electrocatalysts, and therefore a method to easily replace anchored molecular catalysts that have degraded could make such electrosynthetic systems more attractive. Here, we apply a non-covalent “click” chemistry approach to reversibly bind molecular electrocatalysts to electrode surfaces via host-guest complexation with surface-anchored cyclodextrins. The host-guest interaction is remarkably strong and allows the flow of electrons between the electrode and the guest catalyst. Electrosynthesis in both organic and aqueous media was demonstrated on metal oxide electrodes, with stability on the order of hours. The catalytic surfaces can be recycled by controlled release of the guest from the host cavities and readsorption of fresh guest. This strategy represents a new approach to practical molecular-based catalytic systems.

Phosphoryl- and Phosphonium-Bridged Viologens as Stable Two- and Three-Electron Acceptors for Organic Electrodes

2020 ◽  
Author(s):  
Colin R. Bridges ◽  
Andryj M. Borys ◽  
Vanessa Béland ◽  
Joshua R. Gaffen ◽  
Thomas Baumgartner
Keyword(s):  
Molecular Weight ◽  
Organic Molecules ◽  
Electrode Materials ◽  
High Energy ◽  
Electron Acceptors ◽  
Low Molecular Weight ◽  
Reduction Potentials ◽  
Organic Electrode ◽  
High Reduction ◽  
High Specific Energy

Low molecular weight organic molecules that can accept multiple electrons at high<br>reduction potentials are sought after as electrode materials for high-energy sustainable batteries. To date their synthesis has been difficult, and organic scaffolds for electron donors significantly outnumber electron acceptors. Herein, we report two highly electron deficient phosphaviologen derivatives from a phosphorus-bridged 4,4-bipyridine and characterize their electrochemical properties. Phosphaviologen sulfide (PVS) and P-methyl phosphaviologen (PVM) accept two and three electrons at high reduction potentials, respectively. PVM can reversibly accept 3 electrons between 3-3.6 V vs. Li/Li+ with an equivalent molecular weight of 102 g/(mol e-) (262 mAh/g), making it a promising scaffold for sustainable organic electrode materials having high specific energy densities.

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