Three-Stage Charge Separation Driven by Multiple Built-In Electric Fields in Novel Bi-MOFs

In photocatalytic systems, although the built-in electric field enhances charge separation, little attention has been paid to the charge migration mechanism induced by this field in monomer materials and charge separation between different segments. Here, focusing on this aspect, we performed a comprehensive analysis of the synergistic effect between built-in electric fields and excited-state behavior in monomer photocatalytic materials for the first time. Novel Bi-MOFs featuring porosity and surface functionalization were synthesized, exhibiting photocatalytic degradation performance superior to that of traditional Bi-MOFs. Based on experimental characterizations and theoretical calculations, macroscale data analysis of BIEF parameters and microscale molecular-level fragment partitioning revealed that BIEF drove the directional migration of photogenerated carriers via the electric field force generated by the potential difference, thereby suppressing carrier recombination. A novel electron-hole-electron three-stage separation phenomenon was identified. This work refined the existing mechanistic understanding of built-in electric fields in monomer materials.