Highly Efficient Noble‐Metal Free Photocatalytic Hydrogen Generation Using Water‐Stable 4,4′‐Vinylenedipyridine‐Based Halide Perovskites

Low-dimensional perovskites show great promise due to their stronger structural stability against external stressors, in particular, moisture. However, the alternance of organic and inorganic layers contributes to form a quantum-well structure leading to the bi-dimensional confinement of the carrier's transport, thus limiting the performances in solar-to-fuel conversion applications. To overcome this issue, the synthesis of the 1D vinylenedipyridine-based (4,4'-VDP)Pb₂X₆ perovskite (X = Br, I), whose specificity is to combine pi-conjugated spacer and cation-pi interactions, is reported. The pi-conjugation electronically connects the inorganic layers, and the cation-pi interactions facilitate stability against water. As a result, exceptional structural and photostability in a large range of aqueous pH is demonstrated. Whereas (4,4'-VDP)Pb₂Br₆ does not show photocatalytic activity toward hydrogen production due to misaligned band energy position with HBr, the iodide counterpart (4,4'-VDP)Pb₂I₆ perovskite produces a substantial amount of hydrogen (1.81 mmol g^-1 after 24 h of photoreaction), without noble metal catalyst utilization and under standard AM 1.5 G illumination conditions.