Hybrid Cobalt Doped-Cerium Oxide as a Multifunctional Nanocatalyst for Various Organic Transformations

Abstract

Development of a low-cost, environmentally benign and robust catalyst for multipurpose industrially relevant organic transformations is highly desirable for the sustainable future of chemical industries. A hybrid cobalt doped-cerium oxide nanocatalyst (Co@CeO2NC) was prepared via simple coprecipitation method using water as the solvent. The characterization of Co@CeO2NC was performed using different techniques such as XRD, TGA, FE-SEM, HR-TEM, EDAX-mapping, BET, and XPS analysis. The structural characterization of the prepared sample by XRD and XPS analysis revealed the presence of the mixed phase of cobalt oxide and cobalt doped-cerium oxide as a hybrid (Co@CeO2NC). Industrially relevant organic transformations such as (i) nitrile formation using aldehyde with hydroxylamine hydrochloride, (ii) reductive amination of aldehydes to form tertiary N,N-dimethyl amines, and (iii) direct acetylation of alcohols/amines with acetic acid were achieved in an excellent manner using Co@CeO2NC hybrid as the multifunctional catalyst. Excellent catalytic activity of Co@CeO2NC was noticed for the conversion of 4-chlorobenzaldehyde to 4-chlorobenzonitrile with 99% conversion and 99% selectivity and 100% conversion of benzaldehyde to N,N-dimethylbenzylamine using DMF as NMe2 source, reductant, and solvent. Moreover, acetylation of 4-methoxybenzyl alcohol and 2-methyl aniline gave excellent conversion and selectivity toward the formation of −O and −N acetyl. The scope of the Co@CeO2NC was further evaluated for other aldehydes, alcohols, and amines with an excellent conversion and high selectivity.

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“…The reaction mixture was subjected to heat at 80°C for 3 h. The suspension was filtered and washed repeatedly with deionized water and then with ethanol. The prepared sample was dried overnight at 110°C and calcined at 300°C for 3 h. [ 46 ]…”

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“…57 Because of the strong oxidation of free radicals, CeO 2 can simulate a variety of enzyme activities, which can be implemented in the fields of sensitive biosensors, 30 pollutant treatment, 58 antibiosis, 51 catalytic cascades, 59 and oxidizing redox reactions in organic synthesis. 60 2.1. POD Activity.…”

“…OVs and free radicals generated by interfacial catalysis play an important role. , The free radicals are produced by the interaction between CeO 2 and substrate and the cycling of Ce 4+ /Ce 3+ , which plays a crucial role commonly including hydroxyl radical (·OH) and superoxide radical (·O 2 •– ) (Figure b) . Because of the strong oxidation of free radicals, CeO 2 can simulate a variety of enzyme activities, which can be implemented in the fields of sensitive biosensors, pollutant treatment, antibiosis, catalytic cascades, and oxidizing redox reactions in organic synthesis …”

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“…The Leuckart-type reaction between wet DMF and aldehydes or ketones arose at 140-160 • C under catalysis with various Lewis [152][153][154] or Brønsted [93] acids (Scheme 49). The use of DCON(CD 3 ) 2 led to the d 7 -reductive amination product [93,152].…”