Amino group promoted photocatalytic hydrogen evolution activity observed in two copper(ii)-based layered complexes

Abstract

Two copper(II)-based layered complexes with or without the amino group, [Cu(HL)₂(NH₂-BDC)]_n (1) and [Cu(HL)₂(BDC)]_n (2) (HL = 4′-(4-hydroxyphenyl)-4,2′:6′,4′′-terpyridine, NH₂-H₂BDC = 2-amino-1,4-benzenedicarboxylic acid and H₂BDC = 1,4-benzenedicarboxylic acid), were solvothermally synthesized and used as photocatalysts to accelerate hydrogen production from water splitting. The amino group modified 1 has exhibited greatly enhanced photocatalytic activity with a hydrogen production rate of 2.34 mmol g⁻¹ h⁻¹ under visible light irradiation, which is almost double that of 2. Density functional theory calculations, electrochemical impedance spectroscopy and transient photocurrent tests demonstrate that the higher catalytic activity of 1 than 2 is a result of the enriched electron density around the Cu^II center by the amino group, which facilitates the charge transfer from the conduction band to the water molecule.