Selective Orbital Coupling-Guided Coordination Engineering of Fe₂CoSe₄/Ti₃C₂ Heterostructures for Efficient Chloride...

Enhancing the selectivity and capacity of chloride capture is a fundamental challenge for high-performance capacitive deionization (CDI). Here, a coordination engineering strategy guided by selective orbital coupling (SOC) theory is proposed for the rational design of superior chloride capture electrodes. A heterostructured Fe₂CoSe₄/Ti₃C₂ featuring coexisting tetrahedral Fe and octahedral Co sites is synthesized as a model platform. This unique dual-site geometry triggers significant charge transfer and electronic modulation, which synergistically tailors the discrete d-orbital states of the active Co sites. The resulting optimization in orbital energy and symmetry enhances selective hybridization with Cl^- 3p orbitals, while the concurrently increased soft-acid character of the Co sites further promotes specific charge-transfer interactions. Consequently, the Fe₂CoSe₄/Ti₃C₂ electrode delivers outstanding desalination performance, including a high salt adsorption capacity of 140.5 mg g^-1, a fast average salt adsorption rate of 5.8 mg g^-1 min^-1, a remarkable charge efficiency of 97.3% (in 2000 mg L^-1 NaCl), and excellent long-term stability. This work not only validates SOC as a powerful design principle for selective CDI electrodes but also establishes a generalizable paradigm to circumvent scaling relations through atomic-scale coordination engineering, paving the way for precisely regulated ion-adsorption energetics in advanced desalination technologies.