Highly-visible-light-driven photocatalysts based on terbium(III) complexes with tetraselenidoantimonate and polyamine mixed ligands

Terbium(III) complexes with anionic selenidoantimonate ligand, [H2tepa][{Tb(tepa)(SbSe4)}2(μ-OH)2] (1) (tepa = tetraethylenepentamine), and [Tb(peha)(SbSe4)]2 (2) (peha = pentaethylenehexamine), were prepared by solvothermal methods in tepa and peha solvents, respectively. The tetrahedral [SbSe4]3− anion coordinated to the Tb3+ ion with a monodentate coordination mode in compound 1, and a bidentate chelating mode in compound 2. Under Xe light irradiation, complexes 1 and 2 exhibited effective photocurrent response with steady current densities of 21.03, and 10.77 μA/cm2, respectively. 1 and 2 were photocatalytically active in the degradation of the organic dye methylene blue in aqueous solution at room temperature. Compound 1 exhibited higher photocatalytic activity than 2 in the degradation due to its stronger photocurrent intensities. The ∙OH radicals and h+ holes were the major reactive substances in the degradation. The in-built redox cycle of Tb(III)/Tb(IV) pair could effectively prompt the h+ hole and ∙OH radical yield, and photocatalytic activities were enhanced.