This study reports a specific bimetallic bismuth-cerium terephthalate metal-organic framework (Bi-Ce(X)-TA MOF) supported on a wood sponge to construct a green photocatalytic reactor for visible-light-driven N2 fixation. Incorporation of Ce ions at an optimal Ce/Bi molar ratio of 0.30 (Bi-Ce(0.30)-TA) significantly enhances visible- light absorption and promotes electron-hole separation. This optimized structure achieves an ammonia yield of 49.6 μmol g 1 h 1, which is 2.3 times higher than that of the pristine Bi-TA. Pyrolysis of Bi-Ce(0.30)-TA MOF produces a fluorite-type Bi-Ce oxide composite embedded in a carbon matrix (Bi0.7Ce0.3O1.7@C). This trans- formation produces a semiconductor with significantly enhanced visible-light absorption that further boosts the NH3 production rate to 131.7 μmol g 1 h 1 with good stability. Stabilization of the normally unstable fluorite Bi oxide phase is achieved via 30% Ce substitution and the presence of oxygen vacancies. In situ Raman spec- troscopy and theoretical calculations suggest that Ce3+/Ce4+ redox centers are proposed to act as electron buffers and bridges for charge transfer, while Bi3+ sites selectively adsorb and activate N2. This cooperative mechanism is consistent with a distal reduction pathway with direct electron transfer. These results provide a generalizable strategy for designing MOF-derived, defect-engineered photocatalysts, highlighting Bi @C as a promising platform for N2 fixation.

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