Achieving Air/Water Stable and Photocatalytically Active Ge-Containing 2D Halide Perovskites by Organic Spacer Engineering

Photocatalytic reactions mediated by Metal Halide Perovskites (MHPs) semiconductors may be the next big thing in the ever-growing exploitation scenarios of these fascinating materials. To make a real impact in this contest, advancements in the material moisture stability and toxicity are needed. We report here novel germanium-based 2D MHPs which show an intrinsic water-stability realized through organic cation engineering. By incorporating 4-phenylbenzilammonium (PhBz) we demonstrate, by means of extended experimental and computational results, that PhBz2GeBr4 and PhBz2GeI4 can achieve a relevant air and water stability. The creation of composites embedding g-C3N4 allows to provide the first proof-of-concept for light induced hydrogen evolution from water by a 2D Ge-based MHP, thanks to the effective charge transfer at the heterojunction between the two semiconductors. These results pave the way to the intelligent design of intrinsically water stable MHPs phases which are highly demanded in all the applicative fields of MHPs.