State-of-the-Art Aluminum Porphyrin-based Heterogeneous Catalysts for the Chemical Fixation of CO2into Cyclic Carbonates at Ambient Conditions

A series of metalloporphyrin-based hyper-crosslinked polymers (M-HCPs: M=Al, Co, Fe, Mn) has been directly synthesized through Friedel–Crafts alkylation reactions. The M-HCPs afforded abundant permanent nanopores, high Brunauer–Emmett–Teller (BET) surface area, and exceptional CO2/N2 adsorptive selectivity. The experimental results suggested that the hollow tubular Al-HCP exhibited extraordinary catalytic performance in the solvent-free synthesis of cyclic carbonates from epoxides and CO2 by using tetrabutylammonium bromide as a cocatalyst under mild conditions, which was clearly superior to the corresponding homogeneous analogue. Surprisingly, a high turnover frequency (TOF) value of 14 880 h−1 was achieved with propylene oxide at 100 °C and 3.0 MPa, which was a promising result for industrial production compared with previously reported heterogeneous catalysts. More interestingly, Al-HCP could smoothly catalyze the cycloaddition reaction, producing the corresponding cyclic carbonates by using simulated flue gas (15 % CO2 and 85 % N2 in volume) as the raw material under ambient conditions. Moreover, Al-HCP could be readily recycled and efficiently reused more than ten times, exhibiting excellent stability.