Metal-Organic Frameworks for Gas-Solid Reactive Carbon Dioxide Capture – Photo/Thermochemical Routes

Abstract

Metal-organic frameworks (MOFs) are customizable adsorbents with demonstrated value for point-source and direct air capture of carbon dioxide (CO2). Simultaneously, MOFs are emerging CO2 reduction catalysts. Combining these independent pillars of success leads to the central focus of our review: the application of MOFs for reactive carbon capture (RCC), a process that eliminates intermediate separation, concentration, and transportation of CO2 from the point of capture to the reactor. In the context of the present review, we consider a gas-solid RCC process where in one step, CO2 is loaded on the material and in a second step, a co-reactant is fed to the reactor while energy in the form of heat or light stimulates product formation. Gas-solid RCC on pristine MOFs remains underexplored when compared with post-synthetically modified MOFs, amine-grafted frameworks, and solution-phase systems. This review critically assesses the dual functionality (capture and conversion) of MOFs, emphasizing their structural tunability, porosity, and photo/thermal catalytic activity. We systematically discuss central features, including CO2 adsorption, thermochemical and photochemical CO2 reduction pathways, and existing barriers to MOF RCC. We highlight specific features essential to RCC, including CO2 chemisorption, band-gap modulation, and charge-transfer mechanisms for light-driven CO2 reduction, and hydrogen/water activation pathways on MOFs. Finally, recent trends, challenges, and prospects in MOF design for RCC are discussed, offering a critical evaluation of their advantages, limitations, and potential for integrated RCC.