Formation mechanism of three member ring containing 1 microporous zincosilicate rub-17 2 3

11 The crystallization process of RUB-17 (RSN-type), a zeolite-type zincosilicate, was studied in 12 order to shed light on the zeolite crystallization mechanism. The sequence of crystallization 13 events from the formation of the initial gel to the complete transformation into a zeolite-type 14 material was investigated. Complementary methods, including XRD, TG/dTG, Raman, 29Si 15 MAS NMR, SEM, that allowed studying both short and long-range order in the solids were 16 used. RSN-type structure contains 3-, 4-, 5and 6-member rings (MRs) that allowed 17 following the formation of different building units in the course of zeolite formation. The set 18 of experimental data revealed that the three-member ring (3MR) was the unit preferentially 19 formed during the induction period. At this stage of gel evolution the presence of larger rings 20 was not detected. The latter were observed only after the appearance of long-range order in 21 the solid proved by X-ray diffraction analysis. Hence the formation of RSN-type structure 22 was related with the large 3MRs population during the induction stage. 23 24 INTRODUCTION 25 Zeolites and related materials are crystalline solids with well-defined system of channels 26 and/or cavities with size below 2 nm. The elementary building unit is TO4 tetrahedron (T = Si, 27 Al, Ge, Ga, P, Ti, ...). The tetrahedral units are connected via four common oxygen atoms 28 thus forming a three-dimensional framework. Up to now, there are 229 zeolite framework 29 types approved by the structure commission of International Zeolite Association.1 Due to their 30 large structural and compositional diversity, zeolites have different physicochemical 31 properties. They are widely used in modern society with applications ranging from household 32 to chemical process industry. Their most important applications are in the fields of 33