Recent advances in CO2 capture and simultaneous conversion into cyclic carbonates over porous organic polymers having accessible metal sites

The cycloaddition reaction of CO2 and various epoxides is one of the most promising approaches for CO2 fixation. Inspired by the synergistic catalytic mechanism based on the double activation model of an epoxide, it's well documented that most metal-based catalysts often show higher catalytic activities than traditional organocatalysts under identical conditions. As a result, the feasible construction of a series of metal-functionalized porous organic polymers (denoted as metal-POPs) can provide the opportunity for integrating the advantages of homogeneous catalysis for high activity and heterogeneous catalysis for facile recyclability. Indeed, metal-POPs are identified as excellent heterogeneous catalysts for capturing and simultaneously converting CO2 into cyclic carbonates, thereby affording quite high activities and selectivities. This review describes the recent advancements with regard to the design and synthesis of metal-POPs featuring accessible active sites and then discloses the structure-property relationship in metal-catalyzed CO2 cycloaddition reactions with epoxides. From the perspective of the design of task-specific monomers and special connectors, we mainly focus on how to introduce metal species into polymer backbones. Also, we discuss multifunctionalization of metal-POPs through the introduction of functional groups including CO2-philic heteroatoms and ionic moieties. Consequently, current challenges and future research efforts are further elaborated for the requirement of practical industrial applications.