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

In this paper, highly efficient photocatalytic reduction of nitroaromatic compounds was investigated using beta-cyclodextrin (beta-CD) and commercial nano-TiO2 as a host-guest system in water under sunlight irradiation. The nitroaromatic compounds solubilized in water through encapsulation in beta-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 beta-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.