Photocatalytic 2‐Iodoethanol Coupling to Produce 1,4‐Butanediol Mediated by TiO₂ and a Catalytic Nickel Complex

Abstract

Photocatalytic 2‐iodoethanol (IEO) coupling provides 1,4‐butanediol (BDO) of particular interest to produce degradable polyesters. However, the reduction potential of IEO is too negative (−1.9 vs NHE) to be satisfied by most of the semiconductors, and the kinetics of transferring one electron for IEO coupling is slow. Here we design a catalytic Ni complex, which works synergistically with TiO2, realizing reductive coupling of IEO powered by photo‐energy. Coordinating by terpyridine stabilizes Ni2+ from being photo‐deposited to TiO2, thereby retaining the steric configuration beneficial for IEO coupling. The Ni complex can rapidly extract electrons from TiO2, generating a low‐valent Ni capable of reducing IEO. The photocatalytic IEO coupling thus provides BDO in 72 % selectivity. By a stepwise procedure, BDO is obtained with 70 % selectivity from ethylene glycol. This work put forward a strategy for the photocatalytic reduction of molecules requiring strong negative potential.