Surface engineering of TeOx modification on MoVTeNbO creates a high-performance catalyst for oxidation of toluene homologues to aldehydes

The heterogeneous catalytic oxidation of toluene by O-2 is an inherently safe and green route for production of benzaldehyde, but after more than fifty years of effort, it remains a great challenge. Here, we report the best heterogeneous catalyst, TeOx/MoVTeNbO, up to now for the green oxidation of toluene by O-2 to benzaldehyde, balancing the catalyst activity, selectivity, and stability. The deposition of TeOx endows the MoVTeNbO composite oxide with entirely new property for toluene oxidation and the surface engineering mechanism has been fully explained. The discrete TeOx clusters on the surface, shielding the nonselective oxidation sites that interact strongly with the benzene ring of toluene molecule, allows toluene molecule to chemically adsorb to the surface perpendicularly and the methyl is then prone to oxidation to aldehyde on the reshaped selective oxidation sites, where V=O is the main active species responsible for continuously extracting hydrogen from methyl and implanting oxygen to form benzaldehyde. The TeOx clusters participate in this reaction through variable valences and stabilize benzaldehyde by couple interaction with the -CHO group of benzaldehyde, thereby achieving high selectivity to benzaldehyde (>95%). The extended works indicate that the catalytic mechanism is effective in a series of selective oxidation of toluene homologues to corresponding aldehydes.