What Up with MOFs\nin Photocatalysis (?): Exploring\nthe Influence of Experimental Conditions on the Reproducibility of\nHydrogen Evolution Rates

Metal–organic frameworks (MOFs) are regarded as\npromising\nmaterials for energy applications, particularly in photocatalytic\nhydrogen (H<sub>2</sub>) production. This is due to their structural\narchitectures that facilitate charge transfer, and tunable porous\nand light absorption properties. However, the many characteristics\nof MOFs including crystal morphology and sizes, surface facets, porosity,\nlight absorption properties, and optical band gaps, can significantly\ninfluence their photocatalytic activity, presenting challenges in\nachieving reproducibility. In this study, we describe the synthesis\nof five distinct batches of the photoactive MOF, MIL-125-NH<sub>2</sub>, utilizing different synthetic conditions. Solid-state characterization\nconfirmed the purity, porosity, and light absorption properties of\neach MOF batch. Each material was then combined with nano sized Ni<sub>2</sub>P as a cocatalyst, and their photocatalytic activity for H<sub>2</sub> evolution was evaluated. We observed variations in their\nphotocatalytic H<sub>2</sub> evolution rates, which depended on the\nbatch of MIL-125-NH<sub>2</sub> utilized, ranging from the lowest\nrate of 2980 μmol·h<sup>–1</sup>·g<sup>–1</sup> to the highest of 4327 μmol·h<sup>–1</sup>·g<sup>–1</sup>. Notably, different H<sub>2</sub> evolution rates\nwere also observed even when MIL-125-NH<sub>2</sub> was synthesized\nunder identical synthetic conditions but by different students. Our\nresearch highlights the critical relationship between MOF synthesis\nparameterssuch as reaction time, temperature, and precursor\nconcentrationand resulting properties, including particle\nsize, morphology, surface facets, and light absorption characteristics.\nThese factors significantly influence their photocatalytic activity,\nas evidenced by varying H<sub>2</sub> evolution rates. This underscores\nthe importance of optimizing materials synthesis conditions to improve\nreproducibility and efficiency in photocatalytic applications.