Base-assisted activation of phenols in TiO2 surface complex under visible light irradiation

Surface charge-transfer complex formed by TiO 2 and phenols has showed a great potential in visible-light photocatalysis. However, back electron transfer limits the charge transfer efficiency and the activation of phenols in surface complex. Herein, we disclosed the efficient activation of phenols in surface complex by introducing the base. Both homocoupling reactions and butylated hydroxytoluene-trapped experiments clearly demonstrated the generation of phenolic radicals from various lignin-derived substrates. The addition of base caused the blue-shifted absorption of surface complex, while increased the visible light-induced electron excitation from substrate to TiO 2 . Vibrational spectra suggested that the interaction between phenolate and TiO 2 was stronger than the interaction between neutral phenol and TiO 2 . This base-triggered strategy may be conducive to useful transformations or degradation of phenols via surface complex.