Accessibility and strength of H-acceptor hydroxyls of ordered mesoporous silicas probed by pyridine donor

Author(s):Show less -

Alves, Mayara R. ^[1] ; Paiva, Mateus F. ^[1] ; Campos, Pablo T. A. ^[1] ; de Freitas, Elon F. ^[1] ; Clemente, Maria Clara H. ^[1] ; Martins, V, Gesley Alex ; Silveira Jr, Alceu T. ; Cides da Silva, Luis C. ^[2] ; Fantini, Marcia C. A. ^[2] ; Dias, Silvia C. L. ^[3] ; Dias, Jose A. ^[3]

Affiliation

^[1] Univ Brasilia, Inst Quim, Lab Catalise, Campus Univ Darcy Ribeiro, Asa Norte, BR-70910900 Brasilia, DF - Brazil

^[2] Univ Sao Paulo, Inst Fis, Cidade Univ, Rua Matao 1371, BR-05508090 Sao Paulo, SP - Brazil

^[3] Martins, Gesley Alex, V, Univ Brasilia, Inst Quim, Lab Catalise, Campus Univ Darcy Ribeiro, Asa Norte, BR-70910900 Brasilia, DF - Brazil

• Document type: Journal article
• Source: JOURNAL OF POROUS MATERIALS; v. 28, n. 2, p. 323-335, APR 2021.
• Web of Science Citations: 1

Abstract

Ordered mesoporous silica (OMS) is an important and useful material for a variety of applications, including catalysis, adsorption, sensing and controlled drug delivery. The surface chemistry and the silanol groups on OMS pores are key properties for the potential modification and application of this material. This research aimed to synthesize (using standard protocols) and differentiate the accessibility and strength of the H-acceptor Si-OH from FDU-12, SBA-16, MCM-41 and SBA-15 by pyridine (Py) donor, where the first two have cubic pore structures and the last two have hexagonal pore structures. Donor-acceptor properties were assessed by calculation of the surface Si-OH densities by thermogravimetry (TG), H2O-TPD/MS, and(29)Si MAS and CP/MAS NMR. The nature of the Si-OH groups on these materials was determined to be hydrogen-bonding sites using FT-IR spectroscopy of Py adsorption. The reactivity of these silanol groups was probed by Py-TG and slurry microcalorimetry of Py adsorption in cyclohexane. Differences in accessibility and reactivity were discussed considering the total potential sites on the surface (n(OH)) versus the actual sites that can react with the Py molecule (n(Py)). By using microcalorimetry, it was possible to quantitatively distinguish the strength of the sites: The acidity order was approximately the same as the relative amount of silanol groups (Si-OH) and Py on the surface of the OMS materials (alpha(Py)): FDU-12 > MCM-41 >= SBA-16 > SBA-15. (AU)

• FAPESP's process: 14/50928-2 - INCT 2014: Pharmaceutical Nanotechnology: a transdisciplinary approach
• Grantee: Maria Vitória Lopes Badra Bentley
• Support Opportunities: Research Projects - Thematic Grants
• FAPESP's process: 17/17075-4 - INCT 2014 - nanotechnology: a transdisciplinary approach - INCT-NANOFARMA - Proc. n. 2014/50928- 2, NanoSight NS300
• Grantee: Maria Vitória Lopes Badra Bentley
• Support Opportunities: Multi-user Equipment Program