Lewis acid (Ni2+, Co2+/3+ or Zn2+) modified electron-deficient Ir4+ in IrO2/CuO for promoting methane oxidation to ethanol and methanol

Abstract

This work delineates the first attempt to tune the product distribution between methanol and ethanol in the direct oxidation of methane reaction by incorporating Lewis acids Ni²⁺, Co^2+/3+ or Zn²⁺ into IrO₂/CuO. The electrophilicity of Ir⁴⁺ and the (LAS–BAS)/LAS ratio (LAS: Lewis acid sites, BAS: Brønsted acid sites) are demonstrated to be two reactivity descriptors motivating CH₄ activation and ethanol formation, respectively. Electron-deficient Ir⁴⁺ motivates enriched *CH₃ concentration and subsequent C–C coupling for C₂H₄ formation, while the Lewis acid promotes ethanol formation from C₂H₄ involving lattice O and H₂O. The ethanol selectivity presents a quasi-linear relationship with (LAS–BAS)/LAS.