Metal-organic frameworks as heterogeneous catalysts for CO2 cycloaddition: A promising strategy for CO2 mitigation and utilization

Abstract

CO2 is a greenhouse gas that contributes to global warming, ocean acidification, and acid rain. Capturing CO2 and converting it into value-added chemicals and fuels could reduce atmospheric CO2 levels. A promising CO2 conversion route is the cycloaddition (CA) reaction with epoxides to produce cyclic carbonates, which have commercial applications. Metal-organic frameworks (MOFs) show promise as CO2-epoxide CA catalysts due to features like high surface area, porosity for mass transfer, and tunable acidic/basic sites. MOFs with dual Lewis acid/base sites act as bifunctional CA catalysts by activating the epoxide and inserting CO2. The typical Lewis acid sites can act as OMSs (Open metal sites) that have the ability to adsorb and activate the reactant molecules, making it easy to promote charge transfer during the conversion of reactant into products.This review examines porous MOFs using transition metals, lanthanides, and alkaline earth metals as central metal atoms. Catalytic activity depends on metal acidity, defect engineering, and the presence of dual metal sites. According to the literature, the rational design of MOFs allows for the successful catalytic conversion of CO2 into value-added cyclic carbonates.