Atomic Compartmentalization of Quaternary Metals in Thin Single‐Crystal PBA Nanocages Enables Superior CO₂‐to‐Syngas Photoreduction

Conventional multimetallic catalysts, often characterized by randomly mixed metals, tend to exhibit competing interactions and ambiguously defined active sites due to poorly understood synergistic effects. Herein, this challenge is surmounted through atomic compartmentalization, achieving precise organization of Co, Cu, Mn, and Fe into role‐specific atomic niches within ultrathin (8 nm) single‐crystalline nanocages. Advanced characterization reveals a hierarchical synergy: Co serves as the primary CO 2 reduction site, while Fe stabilizes the framework via robust Fe─CN─Co coordination. Cu functions as an atomic electron shuttle, elevating the Co oxidation state to enhance charge transfer and CO 2 activation, while Mn induces lattice strain and nanocage formation, optimizing CO 2 binding and active‐site exposure. This synergistic design yields a higher syngas production rate of V CO = 35.77 mmol·g −1 h −1 , V H2 = 33.96 mmol g −1 h −1 (CO/H 2 ≈1), outperforming many reported Co‐based catalysts, while maintaining stability in cycling test. The work redefines multimetallic catalyst design, demonstrating that atomic‐level precision fosters unparalleled functional complementarity.