Creating chemisorption sites for enhanced CO2 chemical conversion activity through amine modification of metalloporphyrin-based hypercrosslinked polymers

The weak physical adsorption of CO2 in porous organic polymers (POPs) leads to the low utilization of CO2 in catalysis, calling for the need to develop materials to ensure higher adsorption of CO2 to achieve high conversion efficiency. In this regard, hydrazine (HZ) was successfully introduced into metalloporphyrin-based hypercrosslinked polymers (HCPs) by post-modification to create abundant CO2 chemisorption sites in structures for efficient adsorption (Qst value up to 34.7 kJ/mol) and chemical conversion of CO2 under ambient conditions. The HZ-modified material (HCP-TPP-Co-HZ) exhibits high catalytic performance for different molecular sizes of epoxide substrates with excellent yields (reaching 98 % of propylene oxide), much superior than that of HCP-TPP-Co-SO3H (64 %), which can be ascribed to the abundant chemisorption sites for CO2 reactants. Moreover, HCP-TPP-Co-HZ has good stability and shows excellent recycling performance (more than 5 times) for the coupling of CO2 with substituted epoxides at room temperature and atmospheric pressure. This strategy to introduce amine groups as CO2 chemisorption sites has been demonstrated to be a new pathway for the design of efficient HCPs catalysts for chemical conversion of CO2.