Abstract: Anew binuclear cobalt molecular catalyst, namely [Co2(dmgH)4(μ-4,4′-bpy)Cl2](1), had been synthesized by the reaction of [Co-(dmgH)(dmgH2)Cl2] with 4,4′-bipyridine(μ-4,4′-bpy). Its structure and properties were characterized by IR,1H NMR, CV, fluorescence, etc. An efficient homogeneous photocatalytic system was constructed by combination of noble-metal-free cobalt complex as catalyst, Eosin Y (EY2-) dye as photosensitizer and TEOA as sacrificial reagent under visible-light irradiation (λ>420 nm). The maximum H2 yield of (1 488.3±34.5 μmol) ((160.0±3.7) TON vs. 1) and H2 evolution rate of (744.2±17.3) μmol·h-1 were recorded under the optimal conditions with 1 of 3.7×10-4 mol·L-1, EY2- of 4×10-4 mol·L-1, TEOA of 20% (v/v) and pH of 10 in 2 h irradiation. Furthermore, the mechanism of H2 evolution in the homogeneous photolysis system was also briefly discussed. The electron transfer from the excited 1*EY2- to Co catalytic center of complex 1 in the designed system was also confirmed to be thermodynamic feasible.
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