Structural, textural and thermal characterization of a confined nanoreactor with phosphorylated catalytic sites grafted onto a halloysite nanotube lumen
Year: 2020
Authors: Gonzalez Rivera J., Spepi A., Ferrari C., Longo I., Tovar Rodriguez J., Fantechi E., Innocenti C., Pineider F., Vera-Ramírez M. A., Tiné M.R., Duce C.
Autors Affiliation: Univ Pisa, Dept Chem & Ind Chem, Via G Moruzzi 13, I-56124 Pisa, Italy; UOS Pisa, Natl Inst Opt INO, Natl Res Council Italy CNR, Via G Moruzzi 1, I-56124 Pisa, Italy; Univ Florence, Dept Chem Ugo Schiff, Via Lastruccia 3, I-50019 Sesto Fiorentino, FI, Italy; CNR, ICCOM, Via Madonna Piano 10, I-50019 Sesto Fiorentino, FI, Italy; UAMI, Dept Chem, Mexico City 09340, DF, Mexico.
Abstract: Mesoporous materials are very attractive solids for the fabrication of confined nanoreactors since they overcome the problems of diffusion/deactivation shown by microporous structures. In this work, we present the fabrication of a confined nanoreactor obtained by functionalization with phosphoric acid of the empty lumen (diameter 10–15 nm) of halloysite nanotubes (Hal).
Two different halloysite nanoreactors with phosphorylated catalytic sites were prepared by the wet impregnation method followed by thermal activation: 1) phosphate modified Hal (starting with pristine Hal), and 2) phosphate-modified etched Hal (starting with etched Hal obtained by soft-etching pristine Hal using sulphuric acid). The selective grafting of hydrogen phosphate groups onto the aluminol active sites was characterized by solid-state nuclear magnetic resonance (1H, 27Al, 29Si HPDEC and 31P) and Fourier transform-infrared spectroscopies, and thermogravimetric and nitrogen physisorption analyses.
Two different aluminum phosphate (AlOP) binding modes, monodentate (AlOPO(OH)2) and bidentate (AlO)2P(OH)2, with different distributions were observed in both phosphorylated-Hal nanoreactors. The selective functionalization of the internal lumen was confirmed because no interaction (due to SiOP binding mode) was detected between the outer surface of Hal and phosphoric acid.
The confined nanoreactors prepared here preserved the main chemical structure and textural properties of Hal. The analysis of the specific surface area and mesopore size showed that, depending on the starting material, grafting the phosphate groups led to the formation of a monolayer or a polycondensation of phosphate moieties inside the tubular mesopore. However, in both prepared nanoreactors, phosphorylation did not result in saturating the material or pore blocking.
These mesoporous materials could be used in catalysis and in situ nanoparticle synthesis.
Journal/Review: APPLIED CLAY SCIENCE
Volume: 196 Pages from: 105752-1 to: 105752-9
More Information: This work was supported by research funds from the University of Pisa. F. P. and E.F. acknowledge the financial support of PRA_2017_25 (University of Pisa). The authors would also like to thank C. Lanza, A. Barbini and F. Pardini (INO-CNR) for their valuable technical support.KeyWords: Halloysite, Nanoreactor, Mesoporous materials, Phosphoric acidDOI: 10.1016/j.clay.2020.105752Citations: 14data from “WEB OF SCIENCE” (of Thomson Reuters) are update at: 2024-10-27References taken from IsiWeb of Knowledge: (subscribers only)Connecting to view paper tab on IsiWeb: Click hereConnecting to view citations from IsiWeb: Click here