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

• DOI: 10.1021/jacs.2c09867
• Publication Date: 2023-07-07T16:19:21Z
• Authors: Lukas Lätsch; Christoph J. Kaul; Alexander V. Yakimov; Imke B. Müller; Alia Hassan; Barbara Perrone; Sadig Aghazada; Zachariah J. Berkson; Trees De Baerdema...; Andrei-Nicolae Pa...; Karsten Seidel; J. Henrique Teles; Christophe Copéret
• Keywords: Chemical shift; Coupling constant; Signature (topology); Local structure; X-ray absorption spectroscopy

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