Single-Crystalline Layered Bimetallic Halide Superlattices with Sublattice-Directed Redox Catalysis for Overall CO2 Photoreduction

Abstract Periodic coupling of electronically distinct sublattices in layered semiconductor superlattices offers a powerful route to tailor band structures and charge dynamics. Hybrid metal halides provide a chemically programmable platform for constructing such architectures, but existing metal-halide superlattices largely rely on organic spacers that limit intersublattice electronic coupling. Here, we construct the coordination-linked PbCl/CuI superlattices in which bifunctional organic linkers periodically organize electronically active Cu–I arrays in proximity to the Pb–Cl layers. The Cu–I arrays constitute an additional inorganic sublattice that contributes to the band-edge electronic structure and photoinduced charge-transfer processes. Photophysical and theoretical studies reveal that Pb–Cl/Cu–I superlattices promote intersublattice electronic coupling, broadens visible-light absorption, and drives directional electron transfer from Cu–I chains to Pb–Cl layers. This charge redistribution creates electron-enriched Pb2+ centers for CO2 adsorption and activation, while holes are largely retained within the Cu–I sublattice to promote water oxidation. Consequently, these superlattices achieve overall CO2 photoreduction in pure water without photosensitizers or sacrificial agents, which produce CO at a rate 6.5 times higher than that of a physical mixture of the Pb–Cl and Cu–I lattices. With trace Rh loading, the superlattice achieves an apparent quantum yield (AQY) of up to 1.14% at 400 nm with near-unity selectivity, representing the highest reported AQY among metal-halide photocatalysts and one of the leading performances among hybrid inorganic–organic photocatalysts. This work establishes a synthetic design paradigm for electronically coupled heterobimetallic halide superlattices for artificial photosynthesis.