Synergy between Brønsted Acid Sites and Cu/Zn Single-Atom Sites in Zeolite for the Direct Oxidation of Methane

The direct oxidation of methane to liquid oxygenates is challenging due to the high C-H bond activation barrier. While metal sites in zeolites are typically considered the primary active centers, this study reveals that Brønsted acid sites (BAS) are indispensable for CH4 activation. Atomic-level incorporation of Cu and Zn into ZSM-5 tunes Brønsted acid strength and stabilizes the framework, creating a cooperative acid-metal environment that enables a remarkable C1 oxygenates productivity of 41651 μmol gcat.-1 h-1 with nearly 90% selectivity at 70 °C. Through CH4-DRIFTS, in situ EPR, and DFT calculations, we demonstrate that BAS induce polarization of CH4, while Cu and Zn activate H2O2 to generate •OH and •OOH radicals. The •OH radicals cleave polarized CH4 to form •CH3 radicals, which selectively couple with reactive oxygen species to yield CH3OH and HCOOH. This work highlights the critical acid-metal synergy in metal-zeolite catalysts for efficient CH4 valorization under mild conditions.