Turning over on sticky balls: preparation and catalytic studies of surface-functionalized TiO2 nanoparticles

• Published in: RSC advances 2021-02, Vol.11 (10), p.5537-5547
• Main Authors: Freimann, Sven A, Prescimone, Alessandro, Housecroft, Catherine E, Constable, Edwin C
• Format: Article
• Language: English
• Subjects: Absorption spectra; Catalytic activity; Chemistry; Crystal structure; Crystallography; Infrared spectroscopy; Ions; Mass spectra; Mass spectrometry; Nanoparticles; NMR spectroscopy; Oxidation; Phosphonates; Phosphonic acids; Reaction kinetics; Recyclability; Rhodium; Silver chloride; Single crystals; Solid state; Surface chemistry; Thermogravimetric analysis; Titanium dioxide
• ISSN: 2046-2069
• DOI: 10.1039/d0ra09319j

We have investigated the reactivity of rhodium(iii) complex-functionalized TiO2 nanoparticles and demonstrate a proof-of-principle study of their catalytic activity in an alcohol oxidation carried out under aqueous conditions water in air. TiO2 nanoparticles (NPs) have been treated with (4-([2,2′:6′,2′′-terpyridin]-4′-yl)phenyl)phosphonic acid, 1, to give the functionalized NPs (1)@TiO2. Reaction between (1)@TiO2 NPs and either RhCl3·3H2O or [Rh2(μ-OAc)4(H2O)2] produced the rhodium(iii) complex-functionalized NPs Rh(1)2@TiO2. The functionalized NPs were characterized using thermogravimetric analysis (TGA), matrix-assisted laser desorption ionization (MALDI) mass spectrometry, 1H NMR and FT-IR spectroscopies; the single crystal structures of [Rh(1)2][NO3]3·1.25[H3O][NO3]·2.75H2O and of a phosphonate ester derivative were determined. 1H NMR spectroscopy was used to follow the reaction kinetics and to assess the recyclability of the NP-supported catalyst. The catalytic activity of the Rh(1)2@TiO2 NPs was compared to that of a homogeneous system containing [Rh(1)2]3+, confirming that no catalytic activity was lost upon surface-binding. Rh(1)2@TiO2 NPs were able to withstand reaction temperatures of up to 100 °C for 24 days without degradation.