Issue 6, 2025

Organic-free synthesis of silicoaluminophosphate zeotype membranes with tunable framework charge density

Abstract

Microporous crystalline membranes utilizing strong adsorptive affinity for separation, especially at elevated temperatures, are needed for separating mixtures containing polar and nonpolar molecules with similar sizes. Zeotype membranes with tunable framework charge densities (FCDs) may serve as a promising candidate for separating such mixtures under industrially relevant conditions. Typically, synthesis of zeotype membranes requires organic compounds as structure-directing agents (SDAs), increasing synthesis cost and complexity and thus potentially restricting their large-scale use. This work reports, for the first time, organic-free synthesis of silicoaluminophosphate (SAPO) zeotype membranes with LTA topology by secondary growth. By varying framework heteroatom (Si) concentrations, the FCD of LTA-type SAPO membranes was tuned between 0.30 and 0.37 with respect to charge-density matching with the inorganic SDA, Na+ cation. Highly charged SAPO membranes showed good separation performance of ammonia (NH3) over non-polar N2 and H2 gases, with selectivities of 32.5 and 9.9, respectively, and excellent thermal stability over 100 h at 150 °C. This inorganic synthesis strategy might be applicable to the fabrication of other types of zeotype membranes with adjustable compositions for affinity-based separations.

Graphical abstract: Organic-free synthesis of silicoaluminophosphate zeotype membranes with tunable framework charge density

Supplementary files

Article information

Article type
Paper
Submitted
19 Sep 2024
Accepted
20 Dec 2024
First published
03 Jan 2025
This article is Open Access
Creative Commons BY license

J. Mater. Chem. A, 2025,13, 4292-4298

Organic-free synthesis of silicoaluminophosphate zeotype membranes with tunable framework charge density

S. H. Park, B. Sengupta, S. E. Gerami, K. Friedman, R. Lecaros, A. F. M. Ibrahim and M. Yu, J. Mater. Chem. A, 2025, 13, 4292 DOI: 10.1039/D4TA06666A

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