Design of MOF-Derived Cd _{1– <i>x</i>} Zn _<i>x</i> S Solid-Solution Photocatalysts and Evaluation of Hydrogen Production by Photoreforming

The photoreforming of low-value biomass in alkaline aqueous media is a promising route for sustainable hydrogen production because it couples hydrogen evolution with the utilization of abundant organic resources. In such systems, sulfide photocatalysts are attractive because of their relative stability and favorable hydrogen evolution activity; however, their hydrogen production performance remains insufficient. To address this limitation, Cd1–xZnxS solid-solution photocatalysts were synthesized using mixed-cation metal–organic frameworks (MOFs) precursors as a platform for precursor design. A series of Cd–Zn mixed MOFs with different Cd/Zn ratios were prepared using terephthalic acid as the organic linker and converted into the corresponding sulfides by sulfidation. Among the samples, CdZnS-73 showed the highest hydrogen production activity during photoreforming in an alkaline aqueous solution containing α-cellulose under simulated sunlight irradiation, with a hydrogen production rate 7.2 times higher than that of MOF-derived CdS. Furthermore, MOF-derived CdZnS-73 exhibited 9.2 times higher activity than a CdZnS sample synthesized without an MOF precursor. This enhanced activity is likely associated not only with solid-solution formation but also with local structural distortion resulting from the MOF-derived synthesis route. These results demonstrate that mixed-cation MOFs are effective precursors toward the design of highly active sulfide photocatalysts for hydrogen production via alkaline biomass photoreforming.