Phosphonium Salt/Al-Porphyrin Copolymer as Bifunctional Heterogeneous Catalyst for CO2 Conversion to Cyclic Carbonates

The effective chemical valorization of CO2 by means of its conversion into valuable products is now more than ever a topic of considerable interest. It is on that basis that herein we have chosen the conversion of CO2 and epoxides to cyclic carbonates as a convenient route to achieve this goal. A new bifunctional (Lewis acid/nucleophile) heterogeneous material, TSP-AlCl-PhospBr, was designed in order to guarantee a close proximity between the two active sites that can cooperate to the activation and opening of the epoxide ring. The prepared copolymer has been extensively characterized using various spectroscopic and analytical techniques. As a heterogeneous catalyst, it enables efficient chemical conversion of CO2 and epoxides, even at low temperatures, down to 30 °C, without the use of solvents. In particular, the catalyst demonstrates high turnover numbers (TON) and frequency values (TOF). Recyclability studies on TSP-AlCl-PhospBr have shown its stability and reusability for consecutive cycles without the need of reactivation procedures.