H-1, Si-29 and Sn-119 double and triple resonance NMR spectroscopy of the small-pore framework sodium stannosilicate Na2SnSi3O9 center dot 2H(2)O

Author(s)

da Silva, Danilo Antonio ^[1] ; Greiser, Sebastian ^[2] ; Contro, Janine ^[1] ; Medeiros, Vinicius Litrenta ^[1] ; Nery, Jose Geraldo ^[1] ; Jaeger, Christian ^[2]

Affiliation

^[1] UNESP Sao Paulo State Univ, Inst Biosci Letters & Exact Sci, Dept Phys, Campus Sao Jose Rio Preto, BR-15054000 Sao Paulo - Brazil

^[2] BAM Fed Inst Mat Res & Testing, NMR Spect, Div Struct Anal 1 3, Richard Willstaetter Str 11, D-12489 Berlin - Germany

• Document type: Journal article
• Source: SOLID STATE NUCLEAR MAGNETIC RESONANCE; v. 107, JUN 2020.
• Web of Science Citations: 0

Abstract

The small-pore framework sodium stannosilicate AV-10, chemical composition Na2SnSi3O9 center dot 2H(2)O and known crystallographic structure, was synthesized by hydrothermal crystallization. This stannosilicate is built up of a three-dimensional network of corner-shared SiO4 tetrahedra and SnO6 octahedra. The SnO6 sites are linked to six SiO4 tetrahedra (Sn(6Si)) while each of the two crystallographically different SiO4 units are connected to two SnO6 and SiO4 units (Si(2Si,2Sn)). This material was used as model compound for developing a solid-state MAS NMR strategy aimed on the challenges and possibilities for structural studies, particularly considering the short and medium range order to verify the connectivity of SiO4 and SnO6 of such compounds despite the low natural abundances of 4.68% for Si-29 and 8.59% for Sn-119 nuclei as a real challenge. Si-29[Sn-119] and Sn-119[Si-29] REDOR (Rotational-Echo Double-Resonance) NMR measurements after H-1 cross-polarization (CP) were carried out. The REDOR curves show a significant change after the ``normal{''} quadratic short time evolution from which both (i) the shortest internuclear Si-29 - Sn-119 distances (and vice versa) and (ii) the number of corner-sharing SiO4 tetrahedra around the SnO6 octahedra (and vice versa) can be obtained. Based on these data, optimized Si-29 [Sn-119] and Sn-119[29Si] REPT-HMQC (Recoupled Polarization Transfer-Heteronuclear Multiple-Quantum Correlation, again after H-1 CP) experiments were implemented, which directly show those heterogroup connectivity as correlation peaks in a 2D spectrum. This information was also obtained using 2D(29)Si[Sn-119]-J-Coupling NMR experiments. Furthermore, 2D29Si INADEQUATE NMR experiments are also feasible, showing the connectivity of SiO4 tetrahedra. The combination of REDOR, REPT-HMQC, J-Coupling and INADEQUATE experiments yielded a complete analysis of the short and medium range structure of this microporous stannosilicate, in agreement with the previously published structure obtained Ab Initio from powder X-Ray diffraction data (XRD). (AU)

• FAPESP's process: 11/51851-5 - Syntheses and characterization of nanozeolites-enzymes complexes and their use as heterogeneous catalysts in the production of biodiesel by trans esterification of Palm Oil and algae oils (Dunaliella Salina and Haematococcus pluvialis) with ethanol
• Grantee: Jose Geraldo Nery
• Support Opportunities: Regular Research Grants