Topotactic Synthesis of Phosphabenzene-Functionalized Porous Organic Polymers: Efficient Ligands in CO2 Conversion.

Abstract

Progress toward the preparation of porous organic polymers (POPs) with task-specific functionalities has been exceedingly slow-especially where polymers containing low-oxidation phosphorus in the structure are concerned. A two-step topotactic pathway for the preparation of phosphabenzene-based POPs (Phos-POPs) under metal-free conditions is reported, without the use of unstable phosphorus-based monomers. The synthetic route allows additional functionalities to be introduced into the porous polymer framework with ease. As an example, partially fluorinated Phos-POPs (F-Phos-POPs) were obtained with a surface area of up to 591 m2 g-1 . After coordination with Ru species, a Ru/F-Phos-POPs catalyst exhibited high catalytic efficiency in the formylation of amines (turnover frequency up to 204 h-1 ) using a CO2 /H2 mixture, in comparison with the non-fluorinated analogue (43 h-1 ) and a Au/TiO2 heterogeneous catalysts reported previously (<44 h-1 ). This work describes a practical method for synthesis of porous organic phosphorus-based polymers with applications in transition-metal-based heterogeneous catalysis.