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

Abstract

An efficient cobaloxime hydrogen production catalyst has been synthesized through 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 bond 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 on 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. This catalytic system maintained its activity after two recycling experiments, previous activation of the catalyst.