Differentiating the Role of Organic Additives to Assemble Open Framework Aluminosilicate Zeolites Using INS Spectroscopy

Abstract

<div> <p>Presently there is little clarity concerning how organic additives control structure formation in the synthesis of zeolite catalysts and their chemistry. Such ambiguity is a major obstacle towards the synthesis design for new bespoke zeolites with intended applications. Herein, we have applied inelastic neutron scattering (INS) spectroscopy to experimentally probe the organic-framework interactions that are crucial to the structure direction process. With this technique we have studied the dynamics of 18-crown-6 ether, which can be used as an additive to direct the formation of four zeolites: Na-X, EMC-2, RHO and ZK-5. We observe significant softening of the 18-crown-6 ether molecule’s dynamics upon occlusion within a zeolite host, with a strong influence on both the circular and radial vibrational modes. Furthermore, there is a strong correlation between the efficacy of the organic additive and the strength of the organic-framework interactions, which are a consequence of both the framework cavity size and geometry. We propose that the approach used herein should be used to study other zeolites, and hence gain a more comprehensive view of structure directing organic-framework interactions.</p> </div> <br>