Designing Dual-Functional Metal-Organic Frameworks for Photocatalysis

Hydrogen (H2) is an ideal alternative to fossil fuels as it is sustainable and environmentally friendly. Hydrogen production using semiconductor-based materials has been extensively investigated; most studies, however, rely on the use of sacrificial electron donors to consume the photogenerated holes, which wastes their oxidizing potential. Dual-functional photocatalysis (DFP) couples the production of H2 with the oxidation of organic molecules, enabling simultaneous utilization of both photogenerated species. To develop efficient materials for DFP, herein, we investigate the interplay of electron/hole dynamics and photophysical properties of metal-organic frameworks (MOFs) using experimental and computational techniques. Four zirconium based MOFs (UiO-66 analogues) were synthesized using different nitrogenfunctionalized ligands. We used benzenethiol in place of a sacrificial reagent to enable simultaneous H2 production and benzenethiol oxidation to sulfide-based products. We demonstrated that Pt/UiO-66-pz (Pt: platinum nanoparticles, pz: pyrazine) is the most efficient dual-functional photocatalyst as it achieved the highest H2 production rates and second-best benzenethiol conversion. Our results shed light on the complex DFP process, wherein the interplay of light absorption, conductivity, band alignment, and charge separation and transfer capabilities are vital for enhancing the dual-functional photocatalytic activity of MOFs.