Near-infrared photothermally enhanced catalysis for benzene hydroxylation

Abstract

The one-step hydroxylation of benzene into phenol, which balances both energy consumption and environmental protection, represents an emerging approach to replace the normal route requiring multiple steps. However, suitable hydroxylation for the selected product, while avoiding over-oxidation remains a challenge. Herein, β-cyclodextrin (β-CD)-modified gold nanorods (CD-AuNRs), which act as both a near-infrared photothermal heater and phase transfer carrier, were synthesized to catalyze the hydroxylation of benzene in Fenton's reagent aqueous solution under near-infrared light irradiation. The conversion in the hydroxylation reaction reached ca. 1.7 times that under external heating with 90.3% selectivity. The electron paramagnetic resonance spectrum indicated the radical mechanism via the formation of ˙OH. The one-dimensional selective nuclear Overhauser effect magnetic spectrum demonstrated the host–guest inclusion of β-CD and the covalent grafting on CD-AuNRs for improved selectivity. The catalytic recycling experiment showed the sufficient stability of CD-AuNRs against light irradiation and catalytic conditions.