Accelerating HCHO-to-CO2 Conversion of a Zeolite–Ag Tandem Catalyst via Adjusting Metal–Oxygen Lewis Pairs

Abstract

Tandem catalysis represents an ideal strategy for HCHO oxidation. The formation and reactivity of gaseous intermediates are the key point. In this study, we present an innovative approach for achieving accurate regulation of highly active intermediate species by utilizing metal–oxygen (Fe³⁺–O^2–) Lewis pairs in SBA-15 zeolite. The formed Fe³⁺–O^2– pairs have a strong interaction with the C–H bond of HCHO, facilitating its dehydrogenation to generate HCOOH gaseous intermediates with high activation over a Ag catalyst. This strategy is also applicable to other metal–oxygen pairs in the SBA-15 zeolite. The constructed tandem catalyst, composed of Fe-SBA-15 and Ag/SBA-15, achieves efficient HCHO oxidation, the HCHO conversion of which is 100 times (100% versus 1%) at 55 °C than that of the Ag/SBA-15 catalyst with a granule mixture of two components and a mass ratio of 1/2. The proximity of these two components also plays a crucial role in significantly boosting the formaldehyde oxidation efficiency. Moderate intimacy is conducive to strengthening the synergistic effect of the two components. Furthermore, this tandem catalyst exhibits superior performance during a long time test, suggesting promising prospects for practical applications. These results thus provide valuable guidance for designing a bifunctional catalyst for efficient VOCs oxidation.