title: Biaxial Q-shearing of 27Al 3QMAS NMR spectra: insight into the structural disorder of framework aluminosilicates.
abstract: In this contribution, we present the application potentiality of biaxial Q-shearing of (27)Al 3QMAS NMR spectra in the analysis of structural defects of aluminium units in aluminosilicates. This study demonstrates that the combination of various shearing transformations of the recorded (27)Al 3QMAS NMR spectra enables an understanding of the broadening processes of the correlation signals of disordered framework aluminosilicates, for which a wide distribution of (27)Al MAS NMR chemical shifts and quadrupolar parameters (i.e., second-order quadrupolar splitting and quadrupole-induced chemical shifts) can be expected. By combining the suitably selected shearing transformation procedures, the mechanisms of the formation of local defects in aluminosilicate frameworks, including Al/Si substitution effects in the next-nearest neighbouring T-sites, variations in bond angles, and/or variations in the physicochemical nature of charge-balancing counter-ions, can be identified. The proposed procedure has been extensively tested on a range of model aluminosilicate materials (kyanite, γ-alumina, metakaolin, analcime, chabazite, natrolite, phillipsite, mordenite, zeolite A, and zeolite Y).
authors: Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky sq. 2, 162 06 Prague 6, Czech Republic. Electronic address: kobera@imc.cas.cz.
authors: Libor
authors: L
authors: Kobera
authors: Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky sq. 2, 162 06 Prague 6, Czech Republic. Electronic address: brus@imc.cas.cz.
authors: Jiri
authors: J
authors: Brus
authors: J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejskova 2155/3, 182 23 Prague 8, Czech Republic. Electronic address: petr.klein@jh-inst.cas.cz.
authors: Petr
authors: P
authors: Klein
authors: J. Heyrovsky Institute of Physical Chemistry, Academy of Sciences of the Czech Republic, Dolejskova 2155/3, 182 23 Prague 8, Czech Republic. Electronic address: jiri.dedecek@jh-inst.cas.cz.
authors: Jiri
authors: J
authors: Dedecek
authors: Institute of Macromolecular Chemistry, Academy of Sciences of the Czech Republic, Heyrovsky sq. 2, 162 06 Prague 6, Czech Republic. Electronic address: urbanova@imc.cas.cz.
authors: Martina
authors: M
authors: Urbanova
keywords: (27)Al 3QMAS NMR; Aluminosilicates; Biaxial shearing; Disorder; Extra-framework aluminium species; Signal broadening; Zeolites