Sustainable Valorization of Methane into Formaldehyde via Atmospheric Gas–Solid Photothermal Catalysis Using a Diatomic Iron Catalyst

Gas–solid photothermal catalytic pathway for methane (CH4) oxidation to formaldehyde (HCHO) at atmospheric pressure addresses product concentration limitations in high-pressure gas–liquid–solid batch systems. However, catalyst deactivation due to slow product desorption and oxygen replenishment remains a challenge. Here, inspired by methane monooxygenase, Fe2 diatomic anchored ZnO catalyst (Fe2–ZnO) were synthesized to addresses such challenge. The Fe2 diatomic pairs enhance charge separation, promoting C–H bond of CH4 cleavage, while their weak interaction with oxygen species facilitates *HCHO desorption, enabling gaseous HCHO production with the assistance of heat. Additionally, the strong interaction between Fe2 pairs and ZnO enhances charge accumulation around the Fe2 diatomic pairs, facilitating O2 adsorption, activation, and oxygen vacancy replenishment. Thus, the Fe2–ZnO catalyst achieves an HCHO production rate of 31.8 mmol gcat–1 h–1 (71.7% selectivity) and superior stability (<10% activity loss over 50 h). And a concentrated HCHO solution (579.7 μmol mL–1, 1.74 wt %) is obtained via water absorption at 0 °C for 12 h. These findings provide references for the application of diatomic catalysts in CH4 conversion.