Synthesis of an A2BC-type asymmetric zinc phthalocyanine derivative for efficient visible/near-infrared-driven H2 evolution on g-C3N4

By using pi-electron-rich thiophene unit to replace one of the benzenoid rings as electron donor and a carboxylnaphthalene unit as electron acceptor, a novel A(2)BC-type asymmetric zinc phthalocyanine derivative (Zn-di-PcNcTh-2) bearing four diphenylthiophenol substituents as steric hindrance groups is synthesized. The A(2)BC-type asymmetric structure of Zn-di-PcNcTh-2 causes a strongly split Q-band and wide spectral absorption in the visible/near-infrared region. By using it as a sensitizer of Pt-loaded g-C3N4, the spectral response region of g-C3N4 is extended from similar to 450 nm to more than 800 nm, and the corresponding Zn-di-PcNcTh-2-sensitized product delivers an average H2 evolution activity of 232 mu mol h(-1) with an extremely high turnover number of 23187 h(-1) under visible light (lambda >= 420 nm) irradiation. Moreover, robust apparent quantum yield values of 5.53%, 4.09% and 2.35% are attained at 760, 780 and 800 nm near-infrared monochromatic light, respectively. The prominent bathochromic and electronic push-pull effects due to the introduced diphenylthiophenol substituents, pi-electronrich thiophene and carboxyl-naphthalene units benefit the efficient red/near-infrared-driven H-2 evolution of the Zn-di-PcNcTh-2-sensitized g-C3N4.