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A novel method to introduce acidic and basic bi-functional sites in the graphitic carbon nitride for the sustainable catalysis: Cycloaddition, esterification, and transesterification reactions

Abstract

Graphitic carbon nitride was prepared using urea, thiourea, and a mixture of urea-thiourea. Functional carbon nitride was prepared by the reaction of g-C3N4 with aqueous H2SO4. Characterizations revealed that bi-functional, acidic (-SO3H) and basic (–NH2) sites were introduced after the aqueous H2SO4 treatment. Characterizations also revealed that the surface acidity and basicity were influenced by the concentration of aqueous H2SO4 solution. A detailed characterization of the catalyst was made using a series of complementary combination of powder X-ray diffraction, N2 adsorption-desorption, scanning/transmission electron microscopy, thermogravimetric analysis, Fourier transform infrared spectroscopy, elemental analysis, and X-ray photoelectron spectroscopy. Furthermore, the bi-functional nature (acidity/basicity) of the catalyst was investigated with NH3 and CO2 temperature programmed desorption techniques. Activation and utilization of CO2 in the synthesis of cyclic carbonates and quinazoline-2,4(1H,3H)-dione over bi-functional graphitic carbon nitride was investigated. Kinetic and thermodynamic parameters (such as k, Ea, H, G, and S) were calculated for the cycloaddition reaction of CO2 to epichlorohydrin by varying the reaction parameters. Graphitic carbon nitride (prepared with urea-thiourea) treated with 60 wt% aqueous H2SO4 exhibited the highest catalytic activity and selectivity in the synthesis of cyclic carbonates and quinazoline-2,4(1H,3H)-dione. The catalyst was easily recovered and recycled with negligible loss in the activity. In addition to this, catalyst exhibited significantly high activity in the transesterification reaction of cyclic carbonate with methanol and esterification reaction of oleic acid with methanol. The uniquness of this study was to introduce bi-functional (acid-base) sites by treating g-C3N4 with aqueous sulfuric acid, which was confirmed using NH3 and CO2 temperature programmed desorption technique and various other physico-chemical charecterizations techniques mentioned above. Simple and economical synthesis procedure, tuneable functional sites, efficient recyclability, and diverse catalytic activity make this catalyst highly attractive for sustainable catalysis.

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Publication details

The article was received on 26 Apr 2017, accepted on 09 Jun 2017 and first published on 09 Jun 2017


Article type: Paper
DOI: 10.1039/C7SE00223H
Citation: Sustainable Energy Fuels, 2017, Accepted Manuscript
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    A novel method to introduce acidic and basic bi-functional sites in the graphitic carbon nitride for the sustainable catalysis: Cycloaddition, esterification, and transesterification reactions

    S. Samanta and R. Srivastava, Sustainable Energy Fuels, 2017, Accepted Manuscript , DOI: 10.1039/C7SE00223H

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