Two Cu-Based Phosphonate Metal-Organic Frameworks as Efficient Water-Splitting Photocatalysts

Two novel three-dimensional metal-organic frameworks(MOFs)based on the photoactive pyrene tetraphosphonate ligand and copper(denoted as IEF-8 and IEF-9) have been hydrothermally synthesizedand fully characterized (XRD, FTIR, TGA, SEM, XPS, etc.). Their crystalstructures were unveiled by single-crystal X-ray diffraction. Remarkably,these materials exhibit coordinatively unsaturated copper (II) sites,free -PO3H2 and -PO3H acidic groups, and good thermal and chemical stability. Further,their optoelectronic characterization evidenced a photoresponse suitablefor photocatalysis. In this sense, the photocatalytic activity ofpyrene phosphonate MOFs was evaluated for the first time for the challenginghydrogen evolution reaction. In particular, IEF-8 exhibited a catalyticefficiency higher than that of the benchmarked Ti carboxylate photocatalystMIL-125-(Ti)-NH2, producing 1800 mu mol center dot g(-1) after 22 h under UV-vis irradiation in theabsence of any co-catalyst. Furthermore, this material presented goodreusability (at least up to 4 cycles), preserving its activity andstructural integrity.

Automated summary

Two three-dimensional metal-organic frameworks (MOFs) called IEF-8 and IEF-9, based on the pyrene tetraphosphonate ligand and copper, have been successfully synthesized and characterized. These MOFs exhibit good thermal and chemical stability, as well as photoresponse suitable for photocatalysis. Specifically, IEF-8 showed higher catalytic efficiency than the benchmarked Ti carboxylate photocatalyst MIL-125-(Ti)-NH2, producing 1800 mu mol center dot g(-1) of hydrogen after 22 hours of UV-vis irradiation without any co-catalyst.