Abstract—Zeolites are crystalline microporous materials with diverse topologies used ubiquitously in catalysis and separations. However, the targeted synthesis of specific frameworks remains limited by the complexity of crystallization and competition among phases. Here, we introduce a data-driven strategy that integrates high-throughput simulations and SHapley Additive exPlanations (SHAP) analysis to design both organic and inorganic structure-directing agents (OSDA and ISDAs, respectively) for synthesizing small-pore zeolites containing lta-cages. Guided by this framework, we identified 4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane as an optimal OSDA, and tailored alkali/alkaline-earth metal cations to stabilize specific composite building units. We achieved the phase-selective crystallization of RHO, KFI, LTA, and UFI zeolites with record-high Si/Al ratios under hydroxide-mediated conditions without the use of fluoride. The resulting high-silica materials exhibit exceptional hydrothermal stability, outperforming that of conventional analogues. Our results establish a generalizable framework for computational SDA selection and rational synthesis of zeolites with targeted structure and composition.
Zeolites are crystalline, microporous materials widely used in catalysis, separations, and ion 7 exchange due to their unique shape- and size-selective properties1,2. Their performance is dictated 8 by framework topology, which defines pore size, connectivity, and molecular transport. Although 9 thousands of energetically viable zeolite frameworks have been predicted computationally3, fewer 10 than 300 have been synthesized, and only a small fraction have been deployed commercially4,5. A 11 central challenge is the lack of predictive control over zeolite crystallization, as framework 12 formation is governed by complex interactions between organic structure-directing agents 13 (OSDAs), inorganic cations, and the evolving gel environment6. Despite advances in empirical 14 design rules, high-throughput synthesis, and computational calculations of organic-inorganic 15 interactions7, control over zeolite topology, composition, and related attributes, remains largely a 16 trial-and-error process, with limited mechanistic insight into how SDAs steer crystallization 17 pathways8. 18 We recently developed a high-throughput computational framework to predict zeolite synthesis 19 outcomes based on OSDA–framework interaction energies to address this challenge9. This strategy 20 quantifies both the strength and selectivity of host–guest interactions using a templating energy, 21 ET, that combines Boltzmann-weighted averages of OSDA binding energies across known 22 frameworks. ET comprises a competition term, reflecting OSDA preference relative to competing 23 phases, and a directivity term, capturing shape complementarity. By minimizing ET, we identified 24 OSDAs capable of targeting specific frameworks or designed intergrowths, enabling the synthesis 25 of pure-phase materials and intergrowths that were previously inaccessible10,11. While this OSDA-26 centric strategy offers a powerful route to tailor organic–framework interactions, the precise 27 mechanism by which inorganic structure-directing agents (ISDAs) modulate the formation of key 28 composite building units (CBUs) and influence the outcome of framework assembly when both 29 OSDAs and ISDAs are used together remains poorly understood, limiting efforts to fully control 30 phase competition. 31 This limitation is especially pronounced for small-pore zeolites containing lta-cages, such as 32 those with LTA, RHO, KFI, and UFI frameworks. These materials require the simultaneous use 33 of OSDAs and ISDAs during synthesis and are of growing interest for separations and redox 34 catalysis due to their cage-based connectivity and tunable transport properties. The LTA 35 framework exhibits a broad synthesis range across various Si/Al ratios; for example, Cu-36 exchanged high-silica forms are hydrothermally stable and demonstrate excellent ammonia 37 selective catalytic reduction (NH₃-SCR) activity, maintaining performance even after aging at 38 900 °C12,13. However, synthesizing high-silica LTA typically requires fluoride-based routes, 39 presenting environmental, safety, and scalability challenges14,15. Structurally related frameworks 40 such as RHO, KFI, and UFI (Fig. 1a), which also incorporate lta-cages but differ in their secondary 41 building units (Fig. 1b) and connectivity, face similar challenges. Although they can be made using 42 OSDA-mediated strategies, their synthesis remains highly sensitive to the type and concentration 43 of inorganic cations16,17. This strong, yet poorly understood, ISDA dependence limits access to 44 fluoride-free, high-silica compositions, which is critical for improved hydrothermal stability and 45 https://doi.org/10.26434/chemrxiv-2025-d7qzq ORCID: https://orcid.org/0000-0003-0409-2179 Content not peer-reviewed by ChemRxiv. License: CC BY-NC-ND 4.0 3 tuning catalytic activity. As such, a predictive framework that integrates both OSDA and ISDA 1 effects is essential for the rational synthesis of lta-based small-pore zeolites with controlled 2 compositions and topologies. 3 Here, we report an integrated computational–experimental strategy for the rational design and 4 synthesis of small-pore zeolites containing lta-cages, including RHO, KFI, LTA, and UFI. High-5 throughput simulations of OSDA–framework interaction energies were used to screen more than 6 2,000 organic molecules for their ability to stabilize lta-cage motifs. In parallel, ~24,000 synthesis 7 conditions involving inorganic cation compositions were analyzed with SHapley Additive 8 exPlanations (SHAP) and density functional theory (DFT) calculations to capture the influence of 9 ISDAs on the formation of distinct framework topologies and stabilize the resulting phases 10 (Fig. 1c). Guided by these predictions, we successfully synthesized phase-pure RHO, KFI, LTA, 11 and UFI zeolites in hydroxide media, without the use of fluoride, achieving record-high Si/Al 12 ratios and exceptional hydrothermal stability. This work provides a broadly applicable platform 13 for the a priori design of zeolite synthesis conditions, integrating OSDA and ISDA selection to 14 expand accessible zeolite phase space with precise topological control.
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Elsa Olivetti
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