Abstract: Photocatalytic CO₂ reduction into valuable fuels is a promising route to mitigate the energy crisis and greenhouse effect, yet it remains severely hampered by the rapid recombination of photogenerated electron-hole pairs and insufficient CO₂ activation in traditional single-metal photocatalysts. A series of stable bimetallic metal-organic framework (MOF) photocatalysts (MTV-TiM, M=Co, Ni, Fe, Mn) were constructed using preformed NH₂-MIL-125(Ti) as the precursor via a post-synthetic modification strategy. The heterometallic clusters and photosensitive organic linkers provide a platform for photoinduced charge transfer and CO₂ reduction. Among the synthesized materials, MTV-TiNi₂ exhibits a CO evolution rate of 13.59 μmol·g⁻¹·h⁻¹ with 93% CO selectivity without any sacrificial agent. When coupled with the [Ru(bpy)₃]²⁺ photosensitizer, the CO evolution rate is boosted to 39.2 μmol·g^–1·h^–1 with an enhanced CO selectivity of 97%, outperforming the other bimetallic counterparts. The improved performance of MTV-TiNi₂ is associated with efficient charge separation and transport, favorable band alignment, and CO₂ adsorption at the framework surface. Furthermore, surface species assigned to COOH*, CO*, CHO*, and CH₃O* support proposed photocatalytic CO₂ reduction pathways. This work provides a new strategy for designing bimetallic MOF photocatalysts with tailored electronic structures for efficient and selective CO₂ reduction.

Key words: heterometallic MOFs, Ni-Ti bimetallic cluster, post-synthetic modification, photocatalytic CO₂ reduction