Mesostructure engineering decouples the lifetime-selectivity trade-off in methanol-to-aromatics reaction over ZSM-5 catalysts

Low-water Na + /K + ion switching creates tunable ZSM-5 mesostructures. • A decoupled ZSM-5 platform isolates diffusion and confinement effects. • Mesopore topology governs the MTA lifetime-selectivity trade-off. • Core-shell Z5-Na8@K0 couples transport, confinement, and coke accommodation. • Spatially integrated mesopores break the lifetime-selectivity trade-off. Balancing molecular diffusion and spatial confinement is central to designing ZSM-5 catalysts for methanol-to-aromatics (MTA), yet their individual roles are difficult to disentangle because mesostructural changes often couple with variations in composition or acidity. Herein, we construct a mesostructure-regulated ZSM-5 platform with comparable framework composition, acid properties, and Al siting via a low-water, seed-induced synthesis. By simply switching alkali metal ions (Na + vs. K + ) and introducing trace amounts of TPABr, two continuously adjustable mesostructural regimes are obtained: open mesoporous nanocrystal assemblies (Na + system) and confined intracrystalline mesoporous single crystals (K + system). MTA catalysis reveals that these two mesostructural regimes impose intrinsically competing demands. Open mesopores enhance molecular transport and coke accommodation, extending catalyst lifetime, but promote premature olefin desorption and weaken BTX shape selectivity. Confined intracrystalline mesopores act as reaction reservoirs that retain intermediates, boosting aromatization and BTX selectivity, yet they are more prone to internal coke accumulation. This establishes a diffusion-confinement competition that governs the lifetime-selectivity trade-off. Guided by this mechanistic distinction, we further construct Z5-Na8@K0, an intraparticle integration of a diffusion-favorable nanocrystal-assembly core and a confinement-providing shell. This architecture moves the lifetime-selectivity frontier forward, achieving a more favorable balance of stability, aromatics selectivity, and cumulative target-product productivity. This work provides a decoupled platform for elucidating structure-performance relationships in zeolites and sheds new light on the rational catalyst design for complex reactions governed by coupled transport and confinement. Download: Download high-res image (287KB) Download: Download full-size image