Selective valorization of lignin to phenol by direct transformation of C(sp2)–C(sp3) and C–O bonds

Phenol is an important commodity chemical in the industry, which is currently produced using fossil feedstocks. Here, we report a strategy to produce phenol from lignin by directly deconstructing C(sp2)–C(sp3) and C–O bonds under mild conditions. It was found that zeolite catalyst could efficiently catalyze both the direct C(sp2)–C(sp3) bond breakage to remove propyl structure and aliphatic β carbon–oxygen (C(β–)O) bond hydrolysis to form OH group on the aromatic ring. The yield of phenol could reach 10.9 weight % with a selectivity of 91.8%. In this unique route, water was the only reactant besides lignin. A scale-up experiment showed that 4.1 g of pure phenol could be obtained from 50.0 g of lignin. The reaction pathway was proposed by a combination of control experiments and density functional theory studies. This work opens the way for producing phenol from lignin by direct transformation of C(sp2)–C(sp3) and C–O bonds in lignin.