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.