Covalent Linkage Engineering of a Bismuth Iodide Framework for Near‐Infrared‐Driven CO ₂ ‐to‐C ₂ Photoreduction in Aqueous Solution

ABSTRACT

Near‐infrared (NIR)‐driven CO ₂ photoreduction to multi‐carbon products remains highly challenging because effective utilization of low‐energy NIR photons requires not only extended light harvesting but also efficient charge separation and transport, structural robustness, and accessible sites for C–C coupling. Although several bismuth halides exhibit narrow bandgaps and NIR absorption, translating such optical response into productive NIR photochemistry remains largely unexplored. Herein, we construct a covalent‐linked bismuth iodide framework, BiI(tadt) (tadt = 1,3,4‐thiadiazole‐2,5‐dithiolate), in which Bi–S covalent bonds bridge dimeric [Bi ₂ I ₂ ] ⁴⁺ clusters with π‐conjugated tadt ligands to form an electronically delocalized framework. The Bi–S linkages enhance structural robustness, facilitate inorganic–organic orbital hybridization, and extend light absorption into the NIR region with a narrow bandgap of 1.44 eV. Photophysical studies and theoretical calculations reveal that linkage‐mediated electronic coupling promotes carrier transport and NIR response, while adjacent Bi ³⁺ sites within [Bi ₂ I ₂ ] ⁴⁺ clusters facilitate *CO coupling and stabilize key *OCCO intermediates. Consequently, single‐component BiI(tadt) achieves NIR‐driven CO ₂ ‐to‐C ₂ photoreduction in aqueous solution with an apparent quantum yield of 0.14% at 750(± 15) nm. This work demonstrates that covalent engineering of inorganic–organic connectivity bridges NIR absorption and productive multi‐electron photochemistry, providing a design principle for lead‐free metal halide photocatalysts utilizing low‐energy solar photons.