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This work aims to understand how different organosilanes impact the synthesis and properties of Sn-Beta zeolites.

May 7, 2026Open Access

Untangling the Role of Organosilane Functional Groups in the Aerosol-Assisted Hydrothermal Synthesis of Sn-Beta Zeolites

Key Points

This work aims to understand how different organosilanes impact the synthesis and properties of Sn-Beta zeolites.
Utilized aerosol-assisted process to introduce various organosilanes into Sn-Si oxide.
Synthesis of Sn-Beta zeolites through hydrothermal methods with fluoride present.
Characterized zeolites' morphology, pore structure, and catalytic performance through quantitative measurements.
Monopodal organosilanes with two amine groups resulted in the highest Lewis acid density of 225 μmol·g−1 and optimum catalytic performance.
Sn-Beta-2A exhibited a specific surface area of up to 502 m2·g−1 and a crystal size reduction to ~0.9 μm.
Dipodal silane B2A yielded the lowest crystallinity (64%) and Lewis acid density (38 μmol·g−1), with diminished catalytic activity.

Abstract

In this work, various types of organosilanes were introduced into Sn-Si oxide through a simple aerosol process to yield synthesis precursors. Then, a series of Sn-Beta zeolites were successfully synthesized using a hydrothermal method in the presence of fluoride. The influence of amine groups (A, 2A, and 3A), the length of branched chains present in the organosilanes, as well as the use of dipodal silanization agents (B2A) on the morphology, pore structure, acidic properties, coordination state, and content of Sn species in the obtained Sn-Beta zeolite samples was investigated. Compared to the organosilane-free Sn-Beta (crystal size: 1.3 μm; Si/Sn = 119; Lewis acid density: 77 μmol·g−1), all monopodal organosilane-doped samples (Sn-Beta-A, -2A, and -3A) exhibited reduced crystal sizes (~0.9 μm) and increased specific surface areas (up to 502 m2·g−1 for Sn-Beta-2A). UV–Vis spectroscopy showed that Sn-Beta-2A (containing two amine groups) achieved the highest optical bandgap (4.68 eV) and the strongest suppression of extra-framework SnOx species (peak at ~269 nm), indicating the most isolated tetrahedral framework Sn4+ sites. This sample also delivered the highest Lewis acid density (225 μmol·g−1) and the best catalytic performance in the Baeyer–Villiger oxidation of cyclohexanone (39% conversion, TON = 106) and 2-adamantanone (37% conversion, TON = 101). By contrast, the dipodal organosilane (B2A) caused severe steric hindrance, yielding the lowest crystallinity (relative crystallinity 64%), Si/Sn ratio (158), Lewis acid density (38 μmol·g−1), and catalytic activity, despite forming a nanoaggregate morphology with high mesoporosity (V meso = 0.20 cm3·g−1). These quantitative results demonstrate that monopodal organosilanes with two amine groups optimally balance Sn incorporation and textural properties, whereas dipodal silanes hinder framework Sn entry. This study provides clear, numerically grounded guidelines for selecting organosilane functional groups to design high-performance Sn-Beta zeolites.

Untangling the Role of Organosilane Functional Groups in the Aerosol-Assisted Hydrothermal Synthesis of Sn-Beta Zeolites

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