A dye-like ligand-based metal-organic framework for efficient photocatalytic hydrogen production from aqueous solution

A dye-like azo-carboxylic acid was chosen as an organic linker to construct a Gd 3+ based metal-organic framework: [Gd 2 (abtc)(H 2 O) 2 (OH) 2 ]·2H 2 O (Gd-MOF) (H 4 abtc = 3,3′,5,5′-azobenzene tetracarboxylic acid). The ultra-stable Gd-MOF possesses a HOMO-LUMO gap of 2.35 eV determined by UV-vis spectroscopy with an absorption edge at 530 nm, which presents effective photocatalytic activity for hydrogen evolution under UV-vis light illumination due to the porous structure and excellent light absorption of the dye-like ligand. To further enhance the photocatalytic activity, different amounts of Ag (1.0-2.0%) were deposited on Gd-MOF as a co-catalyst. The results of electrochemical impedance spectroscopy (EIS) and photoluminescence spectroscopy (PL) clearly indicate that the reaction proceeds through the electron transfer from Gd-MOF to the deposited Ag. Especially, Ag(1.5)/Gd-MOF exhibits significant improvement in the hydrogen evolution rate, which is about 1.5 times greater compared to that of bare Gd-MOF. A dye-like based Gd-MOF exhibits efficient photocatalytic activity for hydrogen generation without a co-catalyst. Depositing Ag further enhances its activity.