Polybenzoxazine bearing phosphonium and phenol functions catalyzed the cycloaddition of CO2 into epoxide reactions

Abstract

Polybenzoxazine bearing phosphonium and phenol functions was firstly designed, synthesized, and evaluated for the cycloaddition of CO2 into epoxide (CCE) reactions. Benzoxazine monomers intrinsically installed with phosphonium halide moiety were thermally polymerized to obtain phenolic-type polybenzoxazines. The bifunctional polybenzoxazine catalyst promoted CCE reactions at 120 °C within 2 h to afford high yields up to 96% under atmospheric pressure. The catalyst was recycled four times and maintained 92% yield. A possible bifunctional catalytic mechanism composed of hydrogen-bonding activation by phenol and co-catalysis by halide was proposed and validated. The easy preparation of the benzoxazine monomers with variety of catalytic moieties, and one-step fabrication of the polybenzoxazines suggest untapped potential of manifold polymeric catalyst design and applications.