Selective Orbital Coupling‐Guided Coordination Engineering of Fe ₂ CoSe ₄ /Ti ₃ C ₂ Heterostructures for Efficient Chloride Capture in High‐Performance Capacitive Deionization

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 Fe 2 CoSe 4 /Ti 3 C 2 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 − 3 p orbitals, while the concurrently increased soft‐acid character of the Co sites further promotes specific charge‐transfer interactions. Consequently, the Fe 2 CoSe 4 /Ti 3 C 2 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.