Increased production of H2 under visible light by packing CdS in a Ti, Zr-Based metal organic framework

Abstract

Metal organic frameworks (MOFs) are crystalline porous materials, and some of them have been used as photocatalysts for H2 production in the presence of Pt and sacrificial reagents. Herein we report a significantly enhanced production of H2 on mixed CdS and MOF, measured under a 420 nm LED lamp in a N2-saturated aqueous solution containing Na2S and Na2SO3. MIL-125-NH2, UiO-66-NH2, and PCN-415-NH2, which are Ti-, Zr-, and Ti, Zr-based MOFs, respectively, were prepared, followed by a two-step precipitation of CdS. All MOFs were nearly not active, but CdS-loaded MOFs were not only active, but also more active than either CdS or Pt/CdS. Moreover, at 40% CdS loading, the MOF activity was PCN-415-NH2 > MIL-125-NH2 > UiO-66-NH2. N2 adsorption showed that CdS nanoparticles were present in the micropores of MOFs. Then the solid photoluminescence, band parameters, and (photo)electrochemical reactions were measured. Accordingly, a possible mechanism is proposed, involving the electron transfer from CdS to PCN-415-NH2, and the hole transfer from PCN-415-NH2 to CdS. In the reaction process, both CdS and MOF act as photocatalysts, other than co-catalysts. This work shows a simply strategy for enhancing H2 production under visible light.