12-Tungstophosphoric acid niched in Zr-based metal-organic framework: a stable and efficient catalyst for Friedel-Crafts acylation

Heteropolyacids (HPA) are well known for their versatile solid acid catalysis in diverse chemical reactions, however they suffer from low surface area (<10 m2/g) and leaching into the reactions media, which reduce their prospects as industrial catalyst. Herein, a novel hybrid material HPW@Zr-BTC, composed of 12-tungstophoric acid (HPW) and ZrIV-benzene tri-carboxylate (Zr-BTC) metal-organic framework (MOF), was prepared via one-pot solvothermal method. Excellent HPW loading up to 32.3 wt% was achieved, and HPW@Zr-BTC composite proved to be highly stable, besides the crystalline morphology of Zr-BTC was intact. The catalytic activity of the hybrid composite was explored via Friedel-Crafts acylation of anisole with benzoyl chloride. The 28.2 wt% HPW@Zr-BTC showed excellent catalytic performance, with 99.4% anisole conversion and 97.6% yield (pmethoxybenzophenone) under solvent free conditions. Excellent retention of catalytic activity was achieved after at least five consecutive runs due to non-observable HPW leaching. The promising activity and stability of the catalyst forecasted its potential industrial applications.