Solar-Driven Conversion of CO2 to C2 Products by the 3d Transition Metal Intercalates of Layered Lead Iodides

Abstract

Photocatalytic CO₂ reduction to high-value-added C₂₊ products presents significant challenges, which is attributed to the slow kinetics of multi-e^- CO₂ photoreduction and the high thermodynamic barrier for C-C coupling. Incorporating redox-active Co²⁺/Ni²⁺ cations into lead halide photocatalysts has high potentials to improve carrier transport and introduce charge polarized bimetallic sites, addressing the kinetic and thermodynamic issues, respectively. In this study, a coordination-driven synthetic strategy is developed to introduce 3d transition metals into the interlamellar region of layered organolead iodides with atomic precision. The resultant bimetallic halide hybrids exhibit selective photoreduction of CO₂ to C₂H₅OH using H₂O vapor at the evolution rates of 24.9-31.4 µmol g^-1 h^-1 and high selectivity of 89.5-93.6%, while pristine layered lead iodide yields only C₁ products. Band structure calculations and photoluminescence studies indicate that the interlayer Co²⁺/Ni²⁺ species greatly contribute to the frontier orbitals and enhance exciton dissociation into free carriers, facilitating carrier transport between adjacent lead iodide layers. In addition, Bader charge distribution calculations and in situ experimental spectroscopic studies reveal that the asymmetric Ni-O-Pb bimetallic catalytic sites exhibit intrinsic charge polarization, promoting C-C coupling and leading to the formation of the key *OC-CHO intermediate.

Keywords: CO2 photoreduction; coordination polymers; crystal engineering; lead halide hybrids; photocatalysis.