Nano-zirconia-supported sulfonic acid as a novel, highly efficient and recyclable heterogeneous nanocatalyst is reported for the synthesis of multicomponent reactions.

Nano-tungsten trioxide-supported sulfonic acid (n-WSA) was found to be an effective heterogeneous catalyst for the one-pot reaction of aromatic aldehydes, b-dicarbonyl compounds and ammonium acetate to afford 1,4-dihydropyridine derivatives in good to excellent yields. The other main advantages of the present method are short reaction times, simple workup, ease in purification and environmentally benign methodology. The reaction conditions were optimized employing Response Surface Method technique (Central Composite Design (CCD)) which is economically considerable because of the minimum number of experiments required to evaluate the effects of multiple parameters on the response.

Epichlorohydrin has been successfully used for coupling nano metal oxides by covalent linkage. Applying this method, a highly efficient and magnetically separable catalyst was synthesized using n‐Fe3O4 and n‐TiO2. This approach is the extension of the third methodology for magnetization of nanoparticles. Stability and catalytic properties of the novel catalyst was investigated by Fourier transform infrared spectroscopy (FT‐IR), field emission scanning electron microscopy (FE‐SEM), thermogravimetric analysis (TGA), X‐ray diffraction (XRD) and vibrating sample magnetometer (VSM). Also, the catalytic activity and selectivity were tested for the oxidation reaction of sulfides to sulfoxides. The catalyst exhibited superior recyclability and reusability. It accomplished six consecutive runs, thoroughly with negligible loss of activity.

BACKGROUND Semiconductor nanomaterials have gained great attention as potential photocatalysts to promote environmentally benign organic reactions. Degussa P25, known as commercial TiO2, is the most applicable semiconductor photocatalyst. However, the wide band‐gap of TiO2 limits its application. A simple way to address this issue is to form heterojunction structures. RESULTS In the present work, n‐TiO2‐P25@ECH@WO3 heterostructure photocatalyst was synthesized for the first time by a two‐step covalent grafting strategy. In this photocatalyst, two nano‐semiconductors, TiO2‐P25 and WO3 were anchored with epichlorohydrin (ECH) as the covalent linker. The properties of n‐TiO2‐P25@ECH@WO3 were investigated through Fourier‐transform infrared spectroscopy (FTIR), X‐ray powder diffraction (XRD), transmission electron microscopy (TEM), energy dispersive X‐Ray (EDX) and UV‐visible/DRS techniques. Under blue LED light, n‐TiO2‐P25@ECH@WO3 oxidized benzyl alcohol to benzaldehyde with excellent selectivity and high yield. CONCLUSION In this study, n‐TiO2‐P25@ECH@WO3 heterostructure photocatalyst was successfully synthesized and evaluated. ECH as the organic linker stably grafted two nano‐semiconductors, n‐TiO2‐P25 and n‐WO3. The heterojunction that formed between n‐TiO2 and n‐WO3 significantly improved the light absorption performance with a considerable redshift to the visible region. Also, the photocatalyst showed an increased activity compared to individual semiconductors. © 2020 Society of Chemical Industry (SCI)

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