Ligand-Engineered Ru(II) Complexes Direct 1D/2D Halide Perovskite Heterostructure Formation for Efficient CO2 Reduction.

Long- and short-chain amine cations trigger surface exfoliation of 3D lead halide perovskites (LHPs) leading to the formation of low-dimensional (low-D) variants. 3D/2D and 3D/1D mixed or hetero-dimensional perovskites are important for photovoltaic applications for their improved surface passivation and stability of raw perovskite, which are used in photocatalysis. Here, two different, cationic ruthenium complexes facilitated the conversion of 3D LHPs to the desired low-D variants. [Ru(bpy)2(4,4'-dinonyl-2,2'-bpy)]2+ (RBN) produces 2D lead halides and [Ru(bpy)2(4,4'-dimethyl-2,2'-bpy)]2+ (RBM) generates 1D/2D heterostructures via stacking of 0D Cs4PbBr6 nanodiscs. Femtosecond transient absorption spectroscopy indicates efficient photoinduced charge stabilization and establishes the Ru-complex-induced low-D LHP variants as promising photocatalytic platforms to sustain high-energy carriers. These are prerequisites for generating catalytic substrates to reduce CO2 and H+. Practically, the 1D/2D heterostructures show exceptional CO2 reduction to CO with very good generation efficiency (rate: 243.6 µmol g-1 h-1), which is ∼8.7-fold higher compared to the higher dimensional LHPs, due to larger surface area, long diffusion length and pronounced electron transfer. RBN, with a nonyl chain, has specific directional properties that control the growth of the 2D LHP sheet, and RBM (methyl appended) produces the 1D variants via 0D hexagonal nanostructure formation.