Cobaloxime tethered pyridine-functionalized ethylene-bridged periodic mesoporous organosilica as an efficient HER catalyst

Abstract

An efficient cobaloxime hydrogen production catalyst has been synthesized through the coordination of a cobalt complex (Co(dmgH₂)(dmgH)Cl₂) on an ethylene-bridged periodic mesoporous organosilica (PMO) containing pyridine moieties. The effective assembly of cobaloxime units through cobalt–pyridine axial bonds on the porous channels of the PMO was clearly evidenced by different techniques, including ¹³C NMR, Raman, IR and XPS. The catalyst was investigated for the hydrogen evolution reaction in a visible-light activated system in the presence of a photosensitizer (eosin Y) and a sacrificial electron donor (TEOA). It showed a good photocatalytic performance in the HER with a TON of 119 at 6 h, largely exceeding the catalytic activity of the homogeneous counterpart, Co(dmgH)₂pyCl, under the conditions studied. The process was proven to be photocatalytic and heterogeneous. The studied system has the cobaloxime catalyst with the highest turnover reported to date for a heterogeneous catalyst under photocatalytic conditions. After reactivation treatment with the Co(dmgH₂)(dmgH)Cl₂ complex, the catalytic system was able to maintain its activity after two recycling experiments.