β-Cyclodextrin–TiO2: Green Nest for reduction of nitroaromatic compounds

Abstract

In this paper, highly efficient photocatalytic reduction of nitroaromatic compounds was investigated using β-cyclodextrin (β-CD) and commercial nano-TiO₂ as a host–guest system in water under sunlight irradiation. The nitroaromatic compounds solubilized in water through encapsulation in β-CD formed an inclusion complex which was attached to TiO₂ under sunlight irradiation. This ‘guest–host system’ that we call ‘Green Nest’ showed high efficiency for the reduction of nitro compounds to the corresponding amines, and more interestingly, one pot reductive N-formylation and N-acylation from nitroaromatic compounds can be carried out in the presence of triethyl orthoformate, acetic and benzoic anhydride. The β-CD–TiO₂ was characterized by transmission electron microscopy, UV-visible spectra, thermogravimetric analysis, Brunauer–Emmett–Teller measurements, UV-visible diffuse reflectance spectroscopy, and Raman spectroscopy.