Polarization-Ordered Tandem in Superlattice Promoting C-N Photocatalytic Cross-Coupling

Transition metal-catalyzed C-N cross-coupling reactions are pivotal in synthesizing pharmaceuticals and agrochemicals. Nickel catalysts, while cost-effective, suffer from rapid deactivation via reductive elimination, leading to reaction instability. Photocatalysis using photogenerated charge carriers offers a promising solution to mitigate metal catalyst deactivation, yet their efficacy remains constrained by inefficient electron-hole separation, which reduces the overall catalytic performance. Herein, we propose a polarization-ordered tandem strategy to integrate multiple continuous charge carrier drivers into superlattice photocatalysts, enabling efficient charge carrier separation over a broader spatial range. Taking Bi₄TaO₈Cl-Bi₂YO₄Cl superlattice as an example, aberration-corrected electron microscopy and atomic-resolution elemental mapping confirm the successful construction of the superlattice structure. Combined with fluorescence spectroscopy, Kelvin probe spectroscopy, and ultrafast spectroscopy, our results indicate that the ordered polarization tandem between the constituent layers significantly lowers the exciton binding energy, improving carrier transfer efficiency and charge separation. Consequently, efficient electron-hole separation effectively suppresses nickel deactivation during C-N coupling reactions. Bi₄TaO₈Cl-Bi₂YO₄Cl can achieve a high conversion (99%) and selectivity (99%) to couple pyrrolidine and 4-bromobenzonitrile under visible light within 2 h. The presented strategy not only effectively mitigates the deactivation of transition metal catalysts in C-N coupling reactions but also opens new avenues for enhancing the efficiency of traditional photocatalytic processes.