Hollow and microporous catalysts bearing Cr(iii)–F porphyrins for room temperature CO2 fixation to cyclic carbonates

Abstract

Hollow and microporous metal free/Cr-porphyrin networks were prepared via the Sonogashira coupling of metal-free or Cr-tetra(4-ethynylphenyl) porphyrins and 1,4-diiodobenzene on the surface of silica templates followed by silica etching. Zinc was introduced into a hollow and microporous metal free porphyrin network (H–MPN) through post-synthetic modification to form a H–MZnPN. Hollow and microporous Cr(III)–F porphyrin networks (H–MCrPNs) showed the best catalytic activities in room temperature CO₂ fixation with epoxides to cyclic carbonates. In addition, the H–MCrPN could be reused at least for five runs, maintaining the original catalytic activity. The good performance of the H–MCrPN is attributed to its microporosity, the shortened diffusion pathways for substrates due to the hollow structure, and the efficient Lewis acidic activity of Cr(III)–F moieties.