Nanoscale coevolution of large- and small-pore zeolite domains during partial interzeolite transformation enables...

Zeolite catalysts often face a fundamental trade-off between molecular accessibility and shape-selective confinement. Here, we show that this trade-off can be mitigated by accessing kinetically stabilized crystalline FAU-CHA intermediates during partial interzeolite transformation. Pair distribution function analysis reveals the coexistence of FAU- and CHA-derived structural motifs within the materials, consistent with the partial structural reorganization of the FAU framework during interzeolite transformation. In situ FT-IR spectroscopy demonstrates that these intermediates retain the Brønsted acid sites characteristic of both frameworks, whereas transient extra-framework aluminum species emerge and are progressively reincorporated into the zeolite lattice. Quantitative acidity measurements using ammonia and pyridine further show that the intermediates preserve a high density of Brønsted acid sites with markedly enhanced accessibility compared to the fully transformed CHA. Together, these results establish kinetically controlled interzeolite transformation as a route to crystalline zeolitic materials, in which accessibility and confinement are jointly encoded through intimate phase contact, with direct implications for catalytic reactions involving bulky substrates.