DOI: 10.1002/chem.201200875 “Extracting” the Key Fragment in ETS-10 Crystallization and Its Application in AM-6 Assembly Meiling Guo, [a, b] Zhaochi Feng, [a] Guanna Li, [a] Jan P. Hofmann, [c] Evgeny A. Pidko, [d] Pieter C. M. M. Magusin, [d] Qiang Guo, [a, b] Bert M. Weckhuysen, [c] Emiel J. M. Hensen, [d] Fengtao Fan,* [a] and Can Li* [a] Introduction ETS-10 is a microporous titanosilicate composed of octahe- dral [TiO 6 ] and tetrahedral [SiO 4 ] units that was originally discovered in 1989 by Engelhard. [1] It possesses a three-di- mensional pore structure with large 12-membered ring-pore openings. [2] Each [TiO 6 ] unit in its framework bears two neg- ative charges, which are balanced by two Na + and/or K + ions. The interesting optical properties of ETS-10 are the result of the one-dimensional -Ti-O-Ti- wires embedded into the insulating silica matrix. [3–5] Upon irradiation with pho- tons larger than the bandgap, the electrons and holes are generated and migrate through the monoatomic quantum wires to the terminal groups and defects. [6] As such, ETS-10 has inspired much interest as a photocatalyst. [7–9] In addition to its potential photocatalysis applications, ETS-10 has at- tracted considerable attention because of its applicability as a base in catalytic reactions [10–13] and also its pronounced cation-exchange capacity. [14] The isomorphous substitution of Ti with V atoms in ETS-10 results in another important ETS-10-type material, AM-6. [15] It also has attracted much attention because of its semiconducting properties, ferro- magnetism, and microporosity. [16, 17] ETS-10-type materials are among the most sophisticated inorganic solids, microporous materials. [18] Generations of researchers have been trying to understand the assembly mechanisms of microporous zeolites, which might provide opportunities for the synthesis of new zeolites and the devel- opment of new synthetic strategies. Several assembly mecha- nisms that concern the nucleation and crystal growth have been proposed, including the growth from soluble and pre- fabricated units, [19–22] autocatalytic nucleation, [23, 24] and solid– liquid interfacial nucleation. [25, 26] This understanding of the crystallization process at a molecular level coupled with a large body of empirical knowledge has led to new concepts of zeolite synthesis. These include the use of prefabricated zeolite nuclei in the synthesis of mesoporous materials [21] and the utilization of crystal seeds to synthesize beta zeolite with the fast crystallization rate in the absence of organic templates. [27] Compared to these more commonly encountered zeolites, the chemical, structural, and topological properties of ETS- 10 are generally quite different. One aspect is that its syn- thesis involves the use of bulk TiO 2 as the Ti source [28] unlike the molecular precursors employed in the synthesis Abstract: The mechanism of crystalli- zation of microporous titanosilicate ETS-10 was investigated by Raman spectroscopy combined with 29 Si magic- angle spinning (MAS) NMR spectro- scopy, DFT calculations, and SEM imaging. The formation of three-mem- bered ring species is shown to be the key step in the hydrothermal synthesis of ETS-10. They are formed by means of a complex process that involves the interaction of silicate species in the re- action mixture, which promotes the dis- solution of TiO 2 particles. These in- sights into the mechanism of ETS-10 growth led to the successful develop- ment of a new synthesis route to the vanadosilicate AM-6 that involves the use of intermediates that contain three- membered ring species as an initiator. Keywords: crystallization · hydrothermal synthesis · Raman spectroscopy · reaction mechanisms · zeolites [a] M. Guo, Prof.Dr. Z. Feng, Dr. G. Li, Q. Guo, Dr. F. Fan, Prof. Dr. C. Li State Key Laboratory of Catalysis Dalian Institute of Chemical Physics Chinese Academy of Sciences 457 Zhongshan Road Dalian, 116023 (P.R. China) Fax: (+ 86) 41-84694447 E-mail: ftfan@dicp.ac.cn canli@dicp.ac.cn [b] M. Guo, Q. Guo Graduate University of Chinese Academy of Sciences No.19A Yuquanlu Beijing, 100049 (P.R. China) [c] Dr. J. P. Hofmann, Prof. Dr. B. M. Weckhuysen Inorganic Chemistry and Catalysis Debye Institute for NanoMaterials Science Utrecht University, Universiteitsweg 993584 CG Utrecht (The Netherlands) [d] Dr. E. A. Pidko, Dr. P. C. M. M. Magusin, Prof. Dr. E. J. M. Hensen Inorganic Materials Chemistry Schuit Institute of Catalysis Eindhoven University of Technology P.O. Box 513, 5600 MB Eindhoven (The Netherlands) Supporting information for this article is available on the WWW under http://dx.doi.org/10.1002/chem.201200875. Chem. Eur. J. 2012, 00,0–0 # 2012 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim These are not the final page numbers! ÞÞ &1& FULL PAPER