Micro/mesoporous conjugated fluorinated iron-porphyrin polymer: porosity and heterogeneous catalyst for oxidation

Abstract

A conjugated micro/mesoporous polymer based on fluorinated iron-porphyrin, FCMP-1, has been prepared via Sonogashira-Hagihara coupling polymerization. The BET-specific surface area of FCMP-1 is about 440 m2 g−1, and its pore sizes are mainly distributed in 0.81 nm and the range of 2.9–3.4 nm, which show that FCMP-1 is the micro/mesoporous polyporphyrin. The polymer shows moderate uptake for methane (4.23 wt%, 273 K) and toluene (615 mg g−1, 298 K). It was also studied as the heterogeneous oxidation catalyst for the oxidative transformation of substituted toluene to corresponding benzoic acid as well as Baeyer–Villiger oxidation using dioxygen as an oxidant. The yields of substituted benzoic acid are ranged from 77 to 88% by employing FCMP-1 as catalyst. Particularly, the yields of the reactions for producing e-caprolactone (more than 99% selectivity) are ranged from 85 to 98%. The channels derived from the porous structure of Fe-porphyrin network are advantageous for the reactive molecules to contact with the catalytic sites and accelerate the diffusion of reactant and product. When compared with the polymer analogue without fluorinated substituents, FCMP-1 with fluorinated phenyl substituents demonstrates the better catalytic performance and cyclic utilization. The fluorinated phenyl moieties linked to Fe-porphyrins facilitate the transformation, due to their stabilizing effect on porphyrin to restrain the breakdown of the catalyst.