Metal–organic frameworks (MOFs) constructed with mixed ligands have shown great promise in the generation of materials with improved sorption, optical, and electronic properties. With an experimental, spectroscopic, and computational approach, herein, we investigated how the incorporation of different functionalized ligands within the structure of MIL-125-NH2 affects its performance in photocatalytic water reduction. We found that multiligand incorporation within the MOF structure has an impact on the light absorption spectrum and the electronic structure. These combined modifications improve the photocatalytic performance of MIL-125-NH2, thereby increasing the rate of hydrogen evolution reaction. Of the four nanoparticle/MOF photocatalytic systems tested, we showed that the Pt/MIL-125-NH2/(OH)2 system (Pt nanoparticle plus MIL-125-NH2 with amino and dihydroxyl functionalized ligands) outperforms its counterpart Pt/MIL-125-NH2 system, attributed to the enhanced p−π conjugation between the lone pairs of O atoms and their aromatic ligands resulting in a red-shifted absorption spectrum and greater spatial distribution of electron density.

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 nitrogen-functionalized 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.

Bismuth-oxocluster nodes for metal−organic frameworks (MOFs) and coordination networks/polymers are less prolific than other families featuring zinc, zirconium, titanium, lanthanides, etc. However, Bi 3+ is non-toxic, it readily forms polyoxocations, and its oxides are exploited in photocatalysis. This family of compounds provides opportunity in medicinal and energy applications. Here, we show that Bi node nuclearity depends on solvent polarity, leading to a family of Bi x -sulfonate/carboxylate coordination networks with x = 1−38. Larger nuclearity-node networks were obtained from polar and strongly coordinating solvents, and we attribute the solvent's ability to stabilize larger species in solution. The strong role of the solvent and the lesser role of the linker in defining node topologies differ from other MOF syntheses, and this is due to the Bi 3+ intrinsic lone pair that leads to weak node−linker interactions. We describe this family by single-crystal X-ray diffraction (eleven structures), obtained in pure forms and high yields. Ditopic linkers include NDS (1,5naphthalenedisulfonate), DDBS (2,2′-[biphenyl-4,4′-diylchethane-2,1-diyl] dibenzenesulphonate), and NH 2 -benzendicarboxylate (BDC). While the BDC and NDS linkers yield more open-framework topologies that resemble those obtained by carboxylate linkers, topologies with DDBS linkers appear to be in part driven by association between DDBS molecules. An in situ small-angle X-ray scattering study of Bi 38 -DDBS reveals stepwise formation, including Bi 38 -assembly, pre-organization in solution, followed by crystallization, confirming the less important role of the linker. We demonstrate photocatalytic hydrogen (H 2 ) generation with select members of the synthesized materials without the benefit of a co-catalyst. Band gap determination from X-ray photoelectron spectroscopy (XPS) and UV−vis data suggest the DDBS linker effectively absorbs in the visible range with ligand-to-Bi-node charge transfer. In addition, materials containing more Bi (larger Bi 38 -nodes or Bi 6 inorganic chains) exhibit strong UV absorption, also contributing to effective photocatalysis by a different mechanism. All tested materials became black with extensive UV−vis exposure, and XPS, transmission electron microscopy, and X-ray scattering of the black Bi 38 -framework suggest that Bi 0 is formed in situ, without phase segregation. This evolution leads to enhanced photocatalytic performance, perhaps due to increased light absorption.

Burning fossil fuels for energy produces greenhouse gases. Greenhouse gases cause climate change, which harms the environment and all living things. Hydrogen fuel can be used as an energy source instead of fossil fuels. We can produce hydrogen using two natural resources: sunlight and water. Hydrogen fuel is renewable, meaning it will not run out, and environmentally friendly because no greenhouse gases are produced. Materials called metal-organic frameworks (MOFs) can speed up the reaction that produces hydrogen gas. With the help of sunlight, MOFs can break apart water molecules to produce hydrogen gas. We can also break down pollutants if we use dirty water in this reaction. Using MOFs, we can purify water and produce hydrogen gas at the same time! Combining MOFs with sunlight can help solve two global problems: climate change and water pollution.