Co‐Catalyst‐Free Chemical Fixation of CO<sub>2</sub> into Cyclic Carbonates by using Metal‐Organic Frameworks as Efficient Heterogeneous Catalysts
Sandeep Singh Dhankhar, Bharat Ugale, C. M. Nagaraja
Abstract
Abstract The concentration of carbon dioxide (CO 2 ) in the atmosphere is increasing at an alarming rate resulting in undesirable environmental issues. To mitigate this growing concentration of CO 2 , selective carbon capture and storage/sequestration (CCS) are being investigated intensively. However, CCS technology is considered as an expensive and energy‐intensive process. In this context, selective carbon capture and utilization (CCU) as a C1 feedstock to synthesize value‐added chemicals and fuels is a promising step towards lowering the concentration of the atmospheric CO 2 and for the production of high‐value chemicals. Towards this direction, several strategies have been developed to convert CO 2 , a Greenhouse gas (GHG) into useful chemicals by forming C−N, C−O, C−C, and C−H bonds. Among the various CO 2 functionalization processes known, the cycloaddition of CO 2 to epoxides has gained considerable interest owing to its 100% atom‐economic nature producing cyclic carbonates or polycarbonates in high yield and selectivity. Among the various classes of catalysts studied for cycloaddition of CO 2 to cyclic carbonates, porous metal‐organic frameworks (MOFs) have gained a special interest due to their modular nature facilitating the introduction of a high density of Lewis acidic (LA) and CO 2 ‐philic Lewis basic (LB) functionalities. However, most of the MOF‐based catalysts reported for cycloaddition of CO 2 to respective cyclic carbonates in high yields require additional co‐catalyst, say tetra‐n‐butylammonium bromide (TBAB). On the contrary, the co‐catalyst‐free conversion of CO 2 using rationally designed MOFs composed of both LA and LB sites is relatively less studied. In this review, we provide a comprehensive account of the research progress in the design of MOF based catalysts for environment‐friendly, co‐catalyst‐free fixation of CO 2 into cyclic carbonates.