Organic–inorganic hybrid perovskites have gained great attention as promising photocatalysts for hydrogen generation. However, due to their poor stability in water, the use of aqueous hydrohalic acid solutions is specifically required for an efficient hydrogen evolution. Herein, three novel photoactive lead-free hybrid perovskites based on bismuth and triazolium cations (denoted as IEF-15, IEF-16, and IEF-17 (IEF stands for IMDEA energy frameworks)) were synthesized and fully characterized (structural, compositional, optical, etc.). Further, these solids were proposed as photocatalysts for the challenging gas phase overall water splitting (OWS) reaction. Accordingly, IEF-16 thin films exhibited a remarkable photocatalytic activity in both H₂ and O₂ evolution, as a consequence of its appropriate bandgap and energy-band alignment, achieving hydrogen evolution rates of 846 and 360 ${{\text{μ}\mathrm{m}\mathrm{o}\mathrm{l}\cdot \mathrm{g}}_{{\mathrm{H}}_2}}^{-1}$ after 24 h under ultraviolet–visible (UV–vis) irradiation or simulated solar irradiation, respectively. This study additionally highlights the remarkable structural and photochemical stability of IEF-16 under different operational conditions (i.e. water volume, irradiation and temperature), paving the way for green hydrogen production from OWS using perovskite-based photocatalysts.

A novel microporous two-dimensional (2D) Ni-based phosphonate metal-organic framework (MOF; denoted as IEF-13) has been successfully synthesized by a simple and green hydrothermal method and fully characterized using a combination of experimental and computational techniques. Structure resolution by single-crystal X-ray diffraction reveals that IEF-13 crystallizes in the triclinic space group Pī having bi-octahedra nickel nodes and a photo/electroactive tritopic phosphonate ligand. Remarkably, this material exhibits coordinatively unsaturated nickel(II) sites, free -PO₃H₂ and -PO₃H acidic groups, a CO₂ accessible microporosity, and an exceptional thermal and chemical stability. Further, its in-deep optoelectronic characterization evidences a photoresponse suitable for photocatalysis. In this sense, the photocatalytic activity for challenging H₂ generation and overall water splitting in absence of any co-catalyst using UV-Vis irradiation and simulated sunlight has been evaluated, constituting the first report for a phosphonate-MOF photocatalyst. IEF-13 is able to produce up to 2,200 μmol of H₂ per gram using methanol as sacrificial agent, exhibiting stability, maintaining its crystal structure and allowing its recycling. Even more, 170 μmol of H₂ per gram were produced using IEF-13 as photocatalyst in the absence of any co-catalyst for the overall water splitting, being this reaction limited by the O₂ reduction. The present work opens new avenues for further optimization of the photocatalytic activity in this type of multifunctional materials.