NMR Signatures and Electronic Structure of Ti Sites in Titanosilicalite-1 from Solid-State 47/49Ti NMR Spectroscopy.

Although titanosilicalite-1 (TS-1) is among the most successful oxidation catalysts used in industry, its active site structure is still debated. Recent efforts have mostly focused on understanding the role of defect sites and extraframework Ti. Here, we report the 47/49Ti signature of TS-1 and molecular analogues [Ti(OTBOS)4] and [Ti(OTBOS)3(OiPr)] using novel MAS CryoProbe to enhance the sensitivity. While the dehydrated TS-1 displays chemical shifts similar to those of molecular homologues, confirming the tetrahedral environment of Ti consistent with X-ray absorption spectroscopy, it is associated with a distribution of larger quadrupolar coupling constants, indicating an asymmetric environment. Detailed computational studies on cluster models highlights the high sensitivity of the NMR signatures (chemical shift and quadrupolar coupling constant) to small local structural changes. These calculations show that, while it will be difficult to distinguish mono- vs dinuclear sites, the sensitivity of the 47/49Ti NMR signature should enable distinguishing the Ti location among specific T site positions.

Citation

Lukas Lätsch, Christoph J Kaul, Alexander V Yakimov, Imke B Müller, Alia Hassan, Barbara Perrone, Sadig Aghazada, Zachariah J Berkson, Trees De Baerdemaeker, Andrei-Nicolae Parvulescu, Karsten Seidel, J Henrique Teles, Christophe Copéret. NMR Signatures and Electronic Structure of Ti Sites in Titanosilicalite-1 from Solid-State 47/49Ti NMR Spectroscopy. Journal of the American Chemical Society. 2023 Jul 19;145(28):15018-15023

PMID: 37418311

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