Subhabrata Mukhopadhyay

University of Hyderabad

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Samar K. Das

University of Hyderabad

Idan Hod

Ben-Gurion University of the Negev

Olivia Basu

University of Hyderabad

Raya Ifraemov

Ben-Gurion University of the Negev

Ran Shimoni

Ben-Gurion University of the Negev

Chandani Singh

Korea Research Institute of Chemical Technology

Sathish Kumar Kurapati

Chaitanya Bharathi Institute of Technology

Itamar Liberman

Ben-Gurion University of the Negev

Sateesh Mulkapuri

University of Hyderabad

Illya Rozenberg

Ben-Gurion University of the Negev

Cooperative Institutions

University of Hyderabad

Ben-Gurion University of the Negev

The Technological College of Beer Sheva

Center for Nanoscale Science and Technology

Indian Association for the Cultivation of Science

Fudan University

Indian Institute of Science Education and Research, Bhopal

Indian Institute of Science Education and Research Kolkata

Council of Scientific and Industrial Research

Indian Institute of Science Bangalore

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A Keggin Polyoxometalate Shows Water Oxidation Activity at Neutral pH: POM@ZIF‐8, an Efficient and Robust Electrocatalyst

Angewandte Chemie International Edition (2017)

Subhabrata Mukhopadhyay Joyashish Debgupta Chandani Singh Aranya Kar Samar K. Das

Keggin-type polyoxometalate anions [XM12 O40 ]n- are versatile, as their applications in interdisciplinary areas show. The Keggin anion [CoW12 O40 ]6- turns into an efficient and robust electrocatalyst upon its confinement in the well-defined void space of ZIF-8, a metal-organic framework (MOF). [H6 CoW12 O40 ]@ZIF-8 is so stable to water oxidation that it retains its initial activity even after 1000 catalytic cycles. The catalyst has a turnover frequency (TOF) of 10.8 mol O2 (mol Co)-1 s-1 , one of the highest TOFs for electrocatalytic oxygen evolution at neutral pH. Controlled experiments rule out the chances of formation and participation of CoOx in this electrocatalyic water oxidation.

Polyoxometalate

Keggin structure

Oxygen evolution

10.1002/anie.201711920

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Citations (170)

Electrostatic Secondary‐Sphere Interactions That Facilitate Rapid and Selective Electrocatalytic CO₂ Reduction in a Fe‐Porphyrin‐Based Metal–Organic Framework

Angewandte Chemie International Edition (2022)

Ran Shimoni Zhuocheng Shi Shahar Binyamin Yang Yang Itamar Liberman

Abstract Metal–organic frameworks (MOFs) are promising platforms for heterogeneous tethering of molecular CO 2 reduction electrocatalysts. Yet, to further understand electrocatalytic MOF systems, one also needs to consider their capability to fine‐tune the immediate chemical environment of the active site, and thus affect its overall catalytic operation. Here, we show that electrostatic secondary‐sphere functionalities enable substantial improvement of CO 2 ‐to‐CO conversion activity and selectivity. In situ Raman analysis reveal that immobilization of pendent positively‐charged groups adjacent to MOF‐residing Fe‐porphyrin catalysts, stabilize weakly‐bound CO intermediates, allowing their rapid release as catalytic products. Also, by varying the electrolyte's ionic strength, systematic regulation of electrostatic field magnitude was achieved, resulting in essentially 100 % CO selectivity. Thus, this concept provides a sensitive molecular‐handle that adjust heterogeneous electrocatalysis on demand.

Coordination sphere

Integrating sphere

10.1002/anie.202206085

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Citations (49)

Local CO2 reservoir layer promotes rapid and selective electrochemical CO2 reduction

Nature Communications (2024)

Subhabrata Mukhopadhyay Muhammad Saad Naeem G. Shiva Shanker Arnab Ghatak Alagar Raja Kottaichamy

Abstract Electrochemical CO 2 reduction reaction in aqueous electrolytes is a promising route to produce added-value chemicals and decrease carbon emissions. However, even in Gas-Diffusion Electrode devices, low aqueous CO 2 solubility limits catalysis rate and selectivity. Here, we demonstrate that when assembled over a heterogeneous electrocatalyst, a film of nitrile-modified Metal-Organic Framework (MOF) acts as a remarkable CO 2 -solvation layer that increases its local concentration by ~27-fold compared to bulk electrolyte, reaching 0.82 M. When mounted on a Bi catalyst in a Gas Diffusion Electrode, the MOF drastically improves CO 2 -to-HCOOH conversion, reaching above 90% selectivity and partial HCOOH currents of 166 mA/cm 2 (at −0.9 V vs RHE). The MOF also facilitates catalysis through stabilization of reaction intermediates, as identified by operando infrared spectroscopy and Density Functional Theory. Hence, the presented strategy provides new molecular means to enhance heterogeneous electrochemical CO 2 reduction reaction, leading it closer to the requirements for practical implementation.

10.1038/s41467-024-47498-9

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Defect Engineering in a Metal–Organic Framework System to Achieve Super-Protonic Conductivity

Chemistry of Materials (2022)

Olivia Basu Subhabrata Mukhopadhyay Subhajit Laha Samar K. Das

Controlled incorporation of missing-linker defect sites could be achieved in four sister metal–organic frameworks (MOFs) of MOF-808, namely, MOF-808 A–D via modulated synthesis. An impressive enhancement in proton conductivity is observed in these sister MOFs (increase from 10–3 to 10–1 S cm–1) as compared to a highly crystalline, low-in-defect variant of MOF-808. MOF-808 C, having optimized defect density, shows a proton conductivity of 2.6 × 10–1 S cm–1 at 80 °C and 98% relative humidity–the highest value reported to date for pure MOF-based proton conductors without extensive structural modifications. The introduction of defects induces super-protonic conductivity by modifying different properties, like porosity, water sorptivity, and acidity. Furthermore, an assembly of this super proton-conducting MOF with Pt─a versatile hydrogen evolution reaction (HER) catalyst, has been studied with the objective to influence the catalytic activity. This MOF-catalyst assembly was found to have lower overpotential requirements, owing to an increase in local acidity and efficient proton management around the catalyst.

Overpotential

Proton Transport

10.1021/acs.chemmater.2c00654

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Designing UiO-66-Based Superprotonic Conductor with the Highest Metal–Organic Framework Based Proton Conductivity

ACS Applied Materials & Interfaces (2019)

Subhabrata Mukhopadhyay Joyashish Debgupta Chandani Singh Rudraditya Sarkar Olivia Basu

Metal-organic framework (MOF) based proton conductors have received immense importance recently. The present study endeavors to design two post synthetically modified UiO-66-based MOFs and examines the effects of their structural differences on their proton conductivity. UiO-66-NH2 is modified by reaction with sultones to prepare two homologous compounds, that is, PSM 1 and PSM 2, with SO3H functionalization in comparable extent (Zr:S = 2:1) in both. However, the pendant alkyl chain holding the -SO3H group is of different length. PSM 2 has longer alkyl chain attachment than PSM 1. This difference in the length of side arms results in a huge difference in proton conductivity of the two compounds. PSM 1 is observed to have the highest MOF-based proton conductivity (1.64 × 10-1 S cm-1) at 80 °C, which is comparable to commercially available Nafion, while PSM 2 shows significantly lower conductivity (4.6 × 10-3 S cm-1). Again, the activation energy for proton conduction is one of the lowest among all MOF-based proton conductors in the case of PSM 1, while PSM 2 requires larger activation energy (almost 3 times). This profound effect of variation of the chain length of the side arm by one carbon atom in the case of PSM 1 and PSM 2 was rather surprising and never documented before. This effect of the length of the side arm can be very useful to understand the proton conduction mechanism of MOF-based compounds and also to design better proton conductors. Besides, PSM 1 showed proton conductivity as high as 1.64 × 10-1 S cm-1 at 80 °C, which is the highest reported value to date among all MOF-based systems. The lability of the -SO3H proton of the post synthetically modified UiO-66 MOFs has theoretically been determined by molecular electrostatic potential analysis and theoretical p Ka calculation of models of functional sites along with relevant NBO analyses.

Side chain

Proton conductor

10.1021/acsami.9b01121

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Citations (198)

A Keggin Polyoxometalate Shows Water Oxidation Activity at Neutral pH: POM@ZIF‐8, an Efficient and Robust Electrocatalyst

Angewandte Chemie (2017)

Subhabrata Mukhopadhyay Joyashish Debgupta Chandani Singh Aranya Kar Samar K. Das

Abstract Keggin‐type polyoxometalate anions [XM 12 O 40 ] n − are versatile, as their applications in interdisciplinary areas show. The Keggin anion [CoW 12 O 40 ] 6− turns into an efficient and robust electrocatalyst upon its confinement in the well‐defined void space of ZIF‐8, a metal–organic framework (MOF). [H 6 CoW 12 O 40 ]@ZIF‐8 is so stable to water oxidation that it retains its initial activity even after 1000 catalytic cycles. The catalyst has a turnover frequency (TOF) of 10.8 mol O 2 (mol Co) −1 s −1 , one of the highest TOFs for electrocatalytic oxygen evolution at neutral pH. Controlled experiments rule out the chances of formation and participation of CoO x in this electrocatalyic water oxidation.

Polyoxometalate

Keggin structure

Oxygen evolution

10.1002/ange.201711920

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Citations (61)

Photo‐Assisted Electrochemical CO₂ Reduction to CH₄ Using a Co‐Porphyrin‐Based Metal–Organic Framework

Solar RRL (2023)

Raya Ifraemov Subhabrata Mukhopadhyay Idan Hod

Metal–organic frameworks (MOFs) are a promising platform for assembling large concentrations of molecular catalysts on surfaces to drive the electroreduction of CO 2 . Yet until now, these MOF‐based systems were shown to produce only 2‐electron/proton products, i.e., CO or formic acid. Herein, it is demonstrated that a cobalt 5,10,15,20‐tetra(4‐carboxyphenyl) porphyrin (CoTCPP)‐based MOF can produce significant quantities of an 8‐electron/proton CH 4 , via a photo‐assisted electrocatalytic approach. Specifically, detailed electrochemical and spectro‐electrochemical analyses show that the addition of light illumination during electrocatalysis promotes the stabilization of a catalyst‐bound CO intermediate, allowing its further reduction to the final product, CH 4 . Using the photo‐assisted electrocatalysis method, maximum CH 4 Faradaic efficiency of 14% was obtained at a low potential of −0.49 V NHE . Hence, the presented concept provides an additional step toward the design of more efficient MOF‐based electrocatalytic systems.

10.1002/solr.202201068

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Tuning the electrochemical and catalytic ORR performance of C₆₀by its encapsulation in ZIF-8: a solid-state analogue of dilute fullerene solution

Materials Chemistry Frontiers (2021)

Olivia Basu Subhabrata Mukhopadhyay Avik De Anupam Das Samar K. Das

Hassle-free encapsulation of fullerene C 60 in ZIF-8 has been performed to preserve the molecularity and solution-like properties of C 60 in solid-state. The resulting composite shows efficient heterogeneous electrocatalytic oxygen reduction reaction.

Encapsulation

10.1039/d1qm00829c

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Citations (10)

Efficient Electrocatalytic Water Oxidation by Fe(salen)–MOF Composite: Effect of Modified Microenvironment

Inorganic Chemistry (2019)

Subhabrata Mukhopadhyay Olivia Basu Aranya Kar Samar K. Das

An efficient and robust heterogeneous electrocatalyst, FSWZ-8 ((Fe-(salen)(OH) + H4[SiW12O40]·HCl)@ZIF-8) for oxygen evolution reaction (OER) at the neutral pH, was developed by coencapsulation of Fe-salen (i.e., Fe(salen)Cl) and SiW12 (i.e., H4[SiW12O40]) inside the cavity of zeolitic imidazolate framework-8 (ZIF-8) material by an in situ synthesis. Here ZIF-8 functions as a host, Fe-salen as the active catalyst, and SiW12 helps in the charge transport by lowering the overall electrical resistance of the resulting composite system. High turnover frequency (∼5 s-1) and high Faradaic efficiency (∼94%) make the concerned composite an efficient catalyst toward water oxidation. This is the first report of one of the simplest known metal complexes, Fe-salen, to perfrom electrocatalytic OER as a heterogeneous catalyst in the neutral pH. This work also highlights the benefits of coencapsulation of the Keggin polyoxometalate (POM) along with the active catalyst Fe-salen species. Encapsulation of SiW12 results in (i) faster formation of FSWZ-8 composite, (ii) higher loading of Fe-salen, and, most importantly, (iii) lowering of required overpotential for electrochemical OER by more than 150 mV. The Keggin POMs, located as discrete molecular oxides inside the cavity of ZIF-8 as well as on the surface of ZIF-8, facilitate electrical charge conduction in the ZIF-8 matrix and lower the overall charge-transfer resistance.

Polyoxometalate

Imidazolate

Overpotential

Oxygen evolution

Keggin structure

10.1021/acs.inorgchem.9b02745

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Citations (49)

CCDC 1838003: Experimental Crystal Structure Determination

The Cambridge Structural Database (2018)

Chandani Singh Subhabrata Mukhopadhyay Samar K. Das

An entry from the Cambridge Structural Database, the world’s repository for small molecule crystal structures. The entry contains experimental data from a crystal diffraction study. The deposited dataset for this entry is freely available from the CCDC and typically includes 3D coordinates, cell parameters, space group, experimental conditions and quality measures.

Crystal (programming language)

10.5517/ccdc.csd.cc1zplfp

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