Current Trends and Approaches to Boost the Performance of Metal Organic Frameworks for Carbon Dioxide Methanation through Photo/Thermal Hydrogenation: A Review

Because of the increasing energy demand of the growing human population, the world is facing a crisis of depleting fossil fuels as well as huge amounts of CO2 emissions being put into the environment. Therefore, to combat these two major issues, catalytic CO2 hydrogenation is introduced which utilizes the abundant CO2 in the atmosphere and at the same time generates clean fuel and chemicals. Metal organic frameworks (MOFs) are a very attractive catalyst for the conversion of CO2 into CH4 due to their high surface area, tunable chemical composition, high porosity, and well-ordered structures. They are also photoresponsive materials. This review discusses the various strategies and modifications implemented to further ameliorate the thermal, photo-, and photothermal catalytic performance of MOFs. Initially, three main catalytic approaches, namely thermal catalysis, photocatalysis, and photothermal catalysis, are thoroughly discussed to understand the mechanism and the differences between them with their characteristics and limitations. Then, a comprehensive review was carried out on various strategies employed to augment the performance of MOFs for CO2 methanation, such as metal addition and incorporation, MOF templating, surface sensitization, formation of heterojunctions, and organic linker modifications via functionalization. Comparisons between MOF-based catalyst and traditional catalyst were carried out to elucidate the beneficial properties of MOFs toward CO2 methanation. The selectivity control for CH4 production was then extensively reviewed in terms of operating parameters, type of catalyst, and reactor. Finally, the mechanism, pathways, intermediates, and adsorbed species involved for CO2 methanation are thoroughly discussed with the help of diffuse reflectance infrared fourier transform spectroscopy (DRIFTS) analysis and Density Functional Theory (DFT) calculations. Therefore, it is clear that metal organic frameworks are highly promising porous crystalline materials for CO2 methanation reaction and have countless possibilities for further enhancement and development to maximize the production of renewable CH4.