Acidity and stability of Nb(V) active sites doped in SBA-15 and ZrSBA-15: A DFT study
Year: 2024
Type: article
Abstract: Mesoporous silicas are of interest in heterogeneous catalysis due to the structural characteristics of their pores and the catalytic properties that can be adjusted by incorporating heteroatoms. The substitution of Zr and Nb into SBA-15 introduces active sites into the material, making it a potential catalyst for reactions of interest to acid catalysis. However, in computational chemistry, discussions on the properties of acids and metal-support interactions in amorphous silicas functionalized with metals are limited. In this study, to determine the acid strength and charge transfer effects between Zr(IV) and Nb(V) chemical species in mesoporous silica, a representative SBA-15 cluster of type 5-6 was proposed. To this end, Density Functional Theory (DFT) simulations were conducted using the B3LYP/6-31G(d,p)/def2TZVP levels. The model successfully replicated trends from larger clusters, demonstrating that the more grafted onto the silica structure, the greater the acid strength of the active site. Additionally, it was found that ZrSBA-15 structures are more stable than NbSBA-15 and have higher acid strength, a trend that has been observed experimentally. The results also suggest that Nb(V) chemical species are more effectively stabilized in ZrSBA-15 compared to SBA-15, which may be due to the presence of Zr(IV) centers in ZrSBA-15. It is expected to contribute to a better understanding of how support affects the stabilization of active phases, leading to the rational design of silica-based heterogeneous catalysts.
Source: Results in Chemistry
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,490
OpenAlex ID: W4403154173