Metal-organic framework based electrochemical reduction

Electrochemically driven reduction of CO₂ to form liquid alternative fuels holds the potential to provide a route for future carbon neutral energy economy. A variety of molecular catalysts based on metal complexes are capable of electrochemically reducing CO₂. Yet, despite the significant progress in this field, practical realization of molecular catalysts will have to involve a simple and robust way to assemble high concentration of these catalysts in an ordered, reactant-accessible fashion onto a conductive electrode.

Metal-Organic Frameworks (MOFs) show a great promise to be utilized as a platform for heterogenizing CO₂ reduction molecular catalysts. Their unique properties (porosity and flexible chemical functionality), enables us to use MOFs for integrating all the different functional elements needed for efficient catalysts: 1) immobilization of molecular catalysts, ^[1] 2) electron transport elements,^[2] 3) mass transport channels, and 4) modulation of catalyst secondary environment.^[3] Thus, in essence, MOFs could possess all of the functional ingredients of a catalytic enzyme.

Here, we will present our recent study on electrocatalytic CO₂ reduction activity of a Zr-based MOF (UIO-66) incorporating molecular catalysts such as Fe-porphyrin.^[1] A discussion on the factors governing the rate of catalytic reaction and product selectivity will be given.

References:

[1] Hod, I.; Sampson, M. D.; Deria, P.; Kubiak, C. P.; Farha, O. K.; Hupp, J. T. “Fe-Porphyrin Based MOF Films as High-Surface-Concentration, Heterogeneous Catalysts for Electrochemical Reduction of CO2”, ACS Catalysis, 2015, 5, 6302-6309.

[2] Hod, I.; Farha, O. K.; Hupp, J. T. “Modulating the Rate of Charge Transport in Metal–Organic Framework Thin Films Using Host:Guest Chemistry”, Chemical Communications, 2016, 52, 1705-1708.

[3] Hod, I.; Deria, P.; Bury, M.; Mondloch, J. E.; Kung, T. C; So, M.; Sampson, M. D.; Peters, A.; Kubiak, C. P.; Farha, O. K.; Hupp, J. T. “A Porous, Proton Relaying, Metal-Organic Framework Material that Accelerates Electrochemical Hydrogen Evolution”, Nature Communications, 2015, 6, 8304.