Effect of Silver Encapsulation on the Local Structure of Titanosilicate Ets-10

Abstract

Silver(0) nanoparticles stabilized by titanosilicate (ETS-10) framework were synthesized by following a simple two step procedure involving the incorporation of silver(I) (Ag +) ions into ETS-10 matrix via ion-exchange with extra framework Na + and K + cations followed by their reduction with sodium borohydride (NaBH 4) in aqueous medium all at room temperature. Silver(0) nanoparticles dispersed in the ETS-10 matrix were collected as gray powders and characterized by using advanced analytical methods including ICP-OES, P-XRD, XPS, FE-SEM, TEM, HR-TEM, DR-UV-vis, Raman spectroscopies and N 2 adsorption-desorption technique. Overall result shows the formation of silver(0) nanoparticles dispersed within the framework of ETS-10 without causing alteration in ETS-10 lattice and mesopore formation. The changes in the local titanate (TiO 3 2-) structure of ETS-10 resulting from the incorporation of silver(I) ions and formation of silver(0) nanoparticles within the titanosilicate (xTiO 2 (1 - x)SiO 2) framework were extensively studied on silver(I)-exchanged and silver(0) nanoparticles containing samples, separately. Although maintaining of structural integrity of host material had been monitored for silver(I)-ETS-10, detailed Raman analyses of silver(0)-ETS-10 samples showed significant changes in the titanate quantum wires of ETS-10 framework depending on the silver loading. Total collapse of these units was observed in the silver(0)-ETS-10 samples with high silver loading (15 wt.% silver(I)). Moreover, the catalytic application of silver(0)-ETS-10 was demonstrated in the aerobic oxidation of diphenyl carbinol to benzophenone, which showed that silver(0)-ETS-10 is a highly active and selective catalyst in this reaction. Additionally, they were found to be highly stable catalyst for this transformation. © 2012 Elsevier Inc. All rights reserved.