An anionic photo-sensitizer intercalated in a layered double hydroxide: Preparation, characterization and photo-oxidation efficiency
Résumé
The synthesis and complete characterization of layered double hydroxides (LDHs) where 4-benzoyl benzoate is either intercalated or adsorbed has been achieved and their photo-sensitizing efficiency for the oxidation of di-n-butylsulfide has been compared. XRD data are noticeably different for the two materials and the presence of an intercalated new phase is obvious for the first material. Elemental analysis and thermogravimetric analysis (TGA) results indicate that intercalated LDH contains much more benzoyl benzoate than adsorbed LDH, while TGA further suggests stronger interactions between the host and the organic anion in the former case. The Fourier transform/infra red (FT/IR) spectrum of the intercalated sample shows no modification of the carbonyl vibration of the benzoyl benzoate moiety upon intercalation within LDH, whereas the diffuse reflectance UV (DRUV) spectrum is strongly modified relative to that of the adsorbed sample. Both intercalated and adsorbed LDHs proved to be efficient and selective sensitizers for the photo-oxidation of di-n-butylsulfide in oxygenated acetonitrile solution. The intercalated photo-sensitizer was efficiently recycled for three successive runs. According to X-ray photoelectron spectroscopy (XPS) analysis of the material after irradiation, the major drawback of these supported sensitizers is the partial replacement of the benzoate anion within the LDH by sulfate and sulfonate anions arising from sulfide oxidation.