CO2-Philic Fluorinated Porous Organic Polyaminal in Photocatalytic Thiol-Ene Chemistry: Decoding the Effect of F-Atoms

Achieving high uptake and efficient conversion of CO2 under mild reaction conditions over metal-free porous organic material as a catalyst is very demanding in the context of CO2 utilization reaction, which is highly sustainable and environmentally green. This is due to the fixation of abundant CO2 as a renewable C1 source and its significant presence in the atmosphere as a primary greenhouse gas. Herein, we report three triazine-based porous organic polyaminals (POPAs) POPA-1, F-POPA-2, and 5F-POPA-3 through the polycondensation of the tetraamine with three aldehydes containing zero, one, and five fluorine atoms, respectively. Fluorine richness into the polymeric network can boost the CO2-philicity, which reflects in the high catalytic activity of the 5F-POPA-3 material. POPA-1, F-POPA-2, and 5F-POPA-3 exhibited CO2 chemisorption capacity of 0.28, 0.26, and 0.45 mmol/g, respectively. As a proof of concept, the cycloaddition reaction of CO2 on epoxies has been carried out over the POPA materials as a catalyst under mild (80 degrees C, balloon pressure) and solvent-free reaction condition. Among these POPAs, 5F-POPA-3 exhibited optimal epoxide conversation and cyclic carbonate selectivity. Low band gap and n-type semiconductor features of 5F-POPA-3 motivated us to utilize it as a photocatalyst in thiol-ene click reaction for the synthesis of thio-ether bridged bicyclic carbonate, which is a platform chemical for the synthesis of value-added polyhydroxyurethanes.