Spatially Proximate Acid Sites in Zeolites Synergistically Boost Alkane Activation.

The activation of light alkanes on zeolites has long been attributed to strong Brønsted acid sites (BAS), a focus that has constrained further catalyst development. Here, we report that in steamed ZSM-5 zeolites, B2 sites from partial hydrolysis of framework aluminum cooperate with neighboring classical BAS (B1) to establish a proximate acid-site microenvironment that substantially enhances both alkane adsorption and activation. Combining solid-state NMR, in situ FTIR spectroscopy with two-dimensional correlation analysis, and density functional theory calculations, we demonstrate that the neighboring B1/B2 sites exhibit a stronger intrinsic affinity for propane than isolated B1 sites, accelerating its accumulation within the pores, which is attributable to the locally optimized van der Waals interactions tuned by the Al─OH of B2. The resulting cooperative acid sites synergistically entrap alkane molecules and facilitate C─H bond activation, boosting propane conversion from 27.2% to 37.5%. Our findings reveal a mechanism for alkane activation that is driven by proximate acid-site cooperativity rather than conventional acid strength of isolated BAS, opening an avenue for designing efficient zeolite catalysts via microenvironment engineering.