No abstract

No abstract

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.

For the neutralization of chemical warfare agents (CWAs), the generation of an effective catalyst that can be handled safely and applied in personal protective equipment is required. Recently, zirconium-based metal-organic frameworks (Zr-MOFs: UiO-66 and UiO-67) have shown great promise in the degradation of CWAs, including nerve agents. Their catalytic activity is owed to the interplay of both Zr­(IV) Lewis acids and Lewis basic groups in the MOF structure. The latter act as proximal bases that can interact with CWAs and improve the catalytic activity of Zr-MOFs. The powder form of MOFs, though, makes them impractical catalysts, as it is challenging to handle, regenerate, and reuse them. To address this challenge, we have synthesized three Zr-MOFs with Lewis basic amino and pyridine functionalities and shaped them in spherical polymeric beads using the phase inversion method. Using this method, we can generate beads with many polymer and MOF combinations (MOF@polymer). We controlled the MOF loading in these beads, and scanning electron microscopy images revealed that the MOF crystals are evenly distributed in the polymeric matrix, ensuring effective catalytic activity. We used these beads to degrade dimethyl p-nitrophenyl phosphate (DMNP), a simulant for the G-type nerve agent. Using 31P NMR, we showed that UiO-66-NH2@PES and UiO-67-(NH2)2@PES PES: poly­(ether sulfone) beads destruct DMNP to dimethyl phosphate (DMP) with a half-life (t 1/2) of 5.09 and 4.34 min, respectively. Beads made of hydrophobic polymers such as poly­(vinylidene fluoride) (PVDF), polystyrene (PS), and Zr-MOFs with pyridine functionalities show that the quantitative hydrolysis of DMNP requires more time compared to that seen with the UiO-66-NH2@PES beads. Our work highlights the facile shaping of MOF powders into beads that can be easily regenerated with their catalytic activity to be maintained for at least three cycles of use.

Herein we describe the use of a metal-organic framework (MOF) with a composition of [Ni3(pzdc)2(ade)2(H2O)1.5](H2O)1.3, for the selective capture of carbon dioxide (CO2) from wet flue gas followed by its...