Proton-Mediated Host–Guest Interactions Direct Nucleation and Morphology Evolution in Molecular Sieve Crystallization

Here, we elucidate how protons actively gate the nucleation and growth of AlPO₄-<i>n</i> /SAPO-<i>n</i> frameworks. By integrating ultrafast operando two-dimensional (2D) solid-state NMR (acquiring high-quality ¹H–²⁷Al HMQC spectra in just 30 seconds) with density functional theory (DFT) simulations, we resolve a proton-mediated dual-channel gating mechanism: under acidic conditions, protons lower the kinetic barrier for P–O–Al condensation from 0.63 to 0.25 eV while simultaneously increasing the thermodynamic driving force for framework assembly, thereby markedly accelerating nucleation.

Operando NMR further reveals an alternating dominance between water/hydroxyl-driven hydrolysis and OSDA-driven templating, a dynamic gating that directs the conversion of amorphous precursors into ordered nuclei via a reversibly formed interfacial intermediate. Moreover, the protonation effect enables selective facet stabilization by acetate species, steering crystal morphology from cubic to nanoscale sheet-like or rod-like architectures across diverse topologies (AFI, CHA, AEI).