Metal organic frameworks as electrocatalysts for CO2 reduction

Abstract

Metal-Organic Frameworks (MOFs) have received significant attention as porous and crystalline materials with potential in gas storage, catalysis, and separation due to their high surface area, tuneable porosity, and various structural characteristics. MOFs have recently emerged as potential candidates for the electrochemical reduction of CO2, an essential process in mitigating the negative consequences of increasing atmospheric CO2 levels, which contribute to global warming, desertification, and ocean acidification. Electrochemical CO2 reduction offers an environmentally friendly approach to converting CO2 into valuable compounds such as methanol, hydrocarbons, and formic acid. In this study three MOF electrocatalysts were synthesised using a solvothermal method, these were MOF-5, Cu-BTC MOF, and Ir(III)CpCl@COMOC-4 MOF. The synthesized MOFs were characterized using various techniques; including Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and Brunauer-Emmett-Teller (BET) analysis. The XRD results revealed diffractogram patterns consistent with previously reported results for the MOFs. SEM analysis showed distinct morphologies for the MOFs. MOF-5 had a cubic morphology, Cu-BTC MOF had an octahedral morphology and Ir(III)CpCl@COMOC-4 MOF displayed irregular structure characterized by visible pores on the surface. The Cu-BTC MOF had the highest specific surface area of 634 m2/g followed by MOF-5 at 630 m2/g and lastly Ir(III)CpCl@COMOC-4 MOF at 273 m2/g. Electrochemical catalysis using cyclic voltammetry, revealed CO2 reduction capabilities across all three MOFs. The CO2 reduction process was indicated by a shift in the MOF redox peaks in the presence of CO2 with increase currents. Differential electrochemical mass spectrometry (DEMS) is required to validate the product(s) formed. The findings indicate that the MOFs show promise as electrocatalysts for CO2 reduction underscoring their potential as candidates for environmentally friendly CO2 conversion technology.