Coordination Anions Dimensionality-Engineered Dual-Atom Catalysts for Enhanced Fenton-Like Reactions: 3D Coordination Induced Spin-State Transition

Dual-atom catalysts (DACs) have shown significant application potential in Fenton-like reactions. However, effectively modulating their electronic structure and fully understanding the mechanisms driving their high catalytic activity remain challenging. Herein, we propose a coordination anions dimensionality engineering strategy to synthesize biomass-derived dual-atom FeCo-N4O1C catalysts, in which Fe and Co atoms are bridged by two-dimensional planar N atoms and a three-dimensional (3D) axial O atom. Experimental data and theoretical calculations reveal that the 3D coordination structure of FeCo-N4O1C induces the spin state of Fe undergo a transition from a low spin state to an intermediate spin state compared with single-atom Fe-N4O1C, resulting in moderate adsorption and desorption of intermediates, thus reducing the energy barriers for generating more singlet oxygen and high-valent cobalt-oxo species during peroxymonosulfate activation. The electron transfer from Co atoms to neighboring Fe atoms through N atoms and 3D axial O atoms can effectively prevent the poisoning of active species. Benefiting from the 3D coordination structure and the synergistic effects of multiple active sites, the catalyst-dose normalized reaction rate constant reaches 14.5 L min-1 g-1 under low peroxymonosulfate concentrations─an improvement of 1 ∼ 2 orders of magnitude over most reported catalysts. The practical applicability of FeCo-N4O1C is demonstrated through nearly 100% pollutant removal during 7 days of continuous operation in a membrane filtration system. This study provides deep insights into the relationship between electronic structure and catalytic performance through spin-state regulation of DACs, and introduces a promising approach for large-scale synthesis of low-cost, highly efficient DACs for Fenton-like reactions.