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

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.