Investigation of Water‐Stable Perovskite DMASnI_xBr_3−x for Photoenzyme Catalysis in Aqueous Solution

The impressive optoelectronic performances of hybrid perovskites have attracted enormous interests. However, the moisture sensitivity of these materials hampers their practical applications. Herein, the lead‐free perovskites of DMASnI_xBr_3−x (DMA = CH₃NH₂CH₃⁺) crystals as photocatalysts for nicotinamide adenine dinucleotide (NADH) regeneration in aqueous solution are engineered. The very high NADH yield (≈100%) is achieved for all the DMASnI_xBr_3−x crystals with tunable bandgaps, which is further coupled with formate dehydrogenase for the production of 320 μM formic acid from CO₂. The density functional theory (DFT) calculations further shed light on the intrinsic water‐stable mechanism of DMASnI₃ perovskite, which is ascribed to the higher water surface adsorption energy, the higher water osmotic energy barrier, and the smaller intralayer spacing inside DMASnI₃ structures by comparing with Pb‐based counterpart. The work can provide new prospects for designing water‐stable hybrid perovskites and further broaden their photocatalytic and optoelectronic applications.