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

Abstract

Achieving high uptake and efficient conversion of CO 2 under mild reaction conditions over metal-free porous organic material as a catalyst is very demanding in the context of CO 2 utilization reaction, which is highly sustainable and environmentally green. This is due to the fixation of abundant CO 2 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 CO 2philicity, which reflects in the high catalytic activity of the 5F-POPA-3 material. POPA-1, F-POPA-2, and 5F-POPA-3 exhibited CO 2 chemisorption capacity of 0.28, 0.26, and 0.45 mmol/g, respectively. As a proof of concept, the cycloaddition reaction of CO 2 on epoxies has been carried out over the POPA materials as a catalyst under mild (80 °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. KEYWORDS: porous organic polyaminals, CO 2 capture, CO 2 /N 2 selectivity, CO 2 utilization, CO 2 to cyclic carbonate, photocatalytic thiol−ene click reaction