Discretizing Cobalt Spin–Orbitals through Tuning the Crystal Symmetry for Zinc–Air Batteries

Regulating the electron-spin state of metal active sites is a rarely cultivated topic for oxygen electrocatalysis. Here, a dual-ligand metal–organic framework (DM) is developed to endow Co sites with D4h crystal symmetry, reconfiguring their orbital degeneracy and electron spin state. The discretized spin–orbital configuration offers the accelerated transformation of the O-related intermediate by accepting electrons via partial d-orbital occupation and mediation of the hydroxyl adsorption strength through electron donation to O p-orbitals. With this orbital flexibility, Co sites serve as “Lewis acid–base” pairs that hasten O redox of oxygen during Zn–air battery cycling, which is validated by operando X-ray absorption spectroscopy and theoretical modeling. Compared to counterparts with different crystal symmetries, Zn–air batteries using the DM electrocatalyst showcase reduced charge–discharge voltage gap and high round-trip energy efficiency at high areal capacity.