Differentiating the role of organic additives to assemble open framework aluminosilicates using INS spectroscopy†
Presently, there is little clarity concerning how organic additives control structure formation in the synthesis of zeolite catalysts. Such ambiguity is a major obstacle towards synthesis design of new bespoke zeolites with intended applications. Herein, we have applied inelastic neutron scattering (INS) spectroscopy to experimentally probe the nature of organic–framework interactions, which are crucial in understanding structure direction. 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 observed 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 size/geometry of the zeolite framework cages and perturbations in the dynamics of the 18C6 oxyethylene chain. We propose that the approach used herein can be used to study other zeolites, and hence gain a more comprehensive view of organic–framework interactions.