RESUMO
Donor-acceptor two-dimensional covalent-organic frameworks (COFs) have great potential as photocatalysts for hydrogen evolution because of their tunable structures, ordered and strong stacking, high crystallinity, and porosity. Herein, an acceptor unit, namely phthalimide, has been employed for the first time to construct COFs. Two donor-acceptor COFs (TAPFy-PhI and TAPB-PhI) have been successfully synthesized via a Schiff base reaction using phthalimide as the acceptor and 1,3,6,8-tetrakis(4-aminophenyl)pyrene (TAPFy) and 1,3,5-tris(4-aminophenyl)benzene (TAPB) as donors. The synthesized COFs exhibited high crystallinity, permanent porosity, excellent chemical stability, suitable band gaps, and broad visible-light absorption. In the presence of ascorbic acid (sacrificial reagent), the TAPFy-PhI COF exhibited an efficient photocatalytic performance with a hydrogen evolution rate of 1763 µmol g-1 h-1. Moreover, the photocatalytic performance was further improved by the addition of Pt (1 wt %) as a cocatalyst, and the hydrogen evolution rate reached 2718 µmol g-1 h-1.
RESUMO
In this work, novel CuGaS2-ZnS p-n type semiconductor nanoheterostructures were synthesized by a solution route, and demonstrated experimentally to be a very promising visible light active photo-catalyst for water-splitting hydrogen production. The construction of CuGaS2-ZnS heterostructures follows a multi-step strategy, employing Cu1.94S nanocrystals first as catalytic assistants for the hetero-growth of ZnS on their surfaces, and then as sacrificial seeds for the formation of CuGaS2. Excitingly, attributed to the efficient charge separation introduced by the p-n heterojunctions, the hydrogen production ability of the CuGaS2-ZnS nanoheterostructures under visible light irradiation is 15 times higher than that of the CuGaS2 component, and comparable to that of the CdS nanophase which is currently regarded as one of the most active visible photo-catalysts for hydrogen generation.
