State-of-the-Art Aluminum Porphyrin-based Heterogeneous Catalysts for the Chemical Fixation of CO2 into 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/N-2 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 turn-over frequency (TOF) value of 14880 h(-1) was achieved with propylene oxide at 100 degrees 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% N-2 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.