Reversible Formation of Silanol Groups in Two-Dimensional Siliceous Nanomaterials under Mild Hydrothermal Conditions

• Published in: Journal of physical chemistry. C Vol. 124; no. 33; pp. 18045 - 18053
• Main Authors: Norton, Angela M, Kim, Donghun, Zheng, Weiqing, Akter, Nusnin, Xu, Yixin, Tenney, Samuel A, Vlachos, Dionisios G, Tsapatsis, Michael, Boscoboinik, J. Anibal
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 20.08.2020
• Subjects: C: Surfaces, Interfaces, Porous Materials, and Catalysis; NANOSCIENCE AND NANOTECHNOLOGY
• ISSN: 1932-7447; 1932-7455
• DOI: 10.1021/acs.jpcc.0c03875

Monitoring the effects of mild hydrothermal conditions, in situ, on siliceous materials remains challenging using surface science techniques, which often require electrically conductive substrates. The emergence of two-dimensional (2-D) siliceous nanomaterials deposited on metal single crystals overcomes this limitation. Here, we use infrared reflection absorption spectroscopy (IRRAS) to study the effects of mild hydrothermal conditions, in situ, on 2-D model systems, namely, all-Si MFI nanosheets supported on Au(111) and a polymorphous bilayer silicate supported on Ru(0001). We find that the formation of silanol groups (SiOH) occurs at 473 and 573 K under a H2O pressure of 3 mbar in the MFI nanosheets, but not in the polymorphous bilayer silicate. The effects of mild hydrothermal conditions are reversible in the MFI nanosheets and do not result in framework degradation. Implications shown here provide a fundamental understanding of the impact of mild hydrothermal conditions on the 2-D siliceous nanomaterials and serve as a starting point when considering these effects on three-dimensional (3-D) ones.