Design Principles for the Synthesis of Self-Pillared ZSM‑5 Zeolite Nanosheets

The
design of next-generation materials for emerging energy and
environmental applications heavily relies on empirical approaches
to direct nonclassical nucleation and crystal growth pathways, polymorphism,
intercrystalline transformations, and seed-assisted growth processes.
A long-standing obstacle to nanoporous materials design is the complexity
of their crystallization, which hinders the development of predictive
models and/or physical descriptors that can guide their synthesis.
In this study, we use a combination of state-of-the-art synthesis,
characterization, and computational design to prepare hierarchical
MFI-type zeolites, which we couple with benchmark catalytic testing
to assess structure-property-performance relationships. These hierarchical
materials are intergrowths of two commercially relevant zeolite frameworks,
MFI and MEL, prepared as self-pillared pentasil (SPP) zeolites through
seed-assisted, organic-free syntheses for which little theoretical
guidance existed. By comparing a large library of zeolite seeds with
different pore sizes, dimensions, and structural composite building
units, we determined the relative impact of seed and silica source
selection, among other synthesis variables. Combined experimental
and computational studies are used to test several hypotheses in literature
to rationalize the choice of seed structure and establish a more robust
selection criteria for seed-assisted synthesis of zeolites. Specifically,
we show that a data-driven approach to develop structural descriptors
correlates to new, facile routes to rationally design SPP zeolites,
addressing knowledge gaps in the fundamental understanding of (non)classical
crystal growth mechanisms that are characteristic of nanoporous aluminosilicates.