Interface Induced Growth and Transformation of Polymer-Conjugated Proto-Crystalline Phases in Aluminosilicate Hybrids: A Multiple-Quantum 23Na‿sup>23Na MAS NMR Correlation Spectroscopy Study.

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• 作者：Jiri Brus ; Libor Kobera ; Martina Urbanova ; Barbora Doušová ; Miloslav Lhotka ; David Koloušek ; Jiří Kotek ; Pavel Čuba ; Jiri Czernek ; Jiří Dědeček
• 刊名：Langmuir
• 出版年：2016
• 出版时间：March 22, 2016
• 年：2016
• 卷：32
• 期：11
• 页码：2787-2797
• 全文大小：658K
• ISSN：1520-5827

文摘

Nanostructured materials typically offer enhanced physicochemical properties because of their large interfacial area. In this contribution, we present a comprehensive structural characterization of aluminosilicate hybrids with polymer-conjugated nanosized zeolites specifically grown at the organic–inorganic interface. The inorganic amorphous Al–O–Si framework is formed by alkali-activated low-temperature transformation of metakaoline, whereas simultaneous copolymerization of organic comonomers creates a secondary epoxide network covalently bound to the aluminosilicate matrix. This secondary epoxide phase not only enhances the mechanical integrity of the resulting hybrids but also introduces additional binding sites accessible for compensating negative charge on the aluminosilicate framework. This way, the polymer network initiates growth and subsequent transformation of protocrystalline short-range ordered zeolite domains that are located at the organic–inorganic interface. By applying an experimental approach based on 2D ²³Na–²³Na double-quantum (DQ) MAS NMR spectroscopy, we discovered multiple sodium binding sites in these protocrystalline domains, in which immobilized Na⁺ ions form pairs or small clusters. It is further demonstrated that these sites, the local geometry of which allows for the pairing of sodium ions, are preferentially occupied by Pb²⁺ ions during the ion exchange. The proposed synthesis protocol thus allows for the preparation of a novel type of geopolymer hybrids with polymer-conjugated zeolite phases suitable for capturing and storage of metal cations. The demonstrated ²³Na–²³Na DQ MAS NMR combined with DFT calculations represents a suitable approach for understanding the role of Na⁺ ions in aluminositicate solids and related inorganic–organic hybrids, particularly their specific arrangement and clustering at interfacial areas.