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Preparation of a Pickering emulsion by modification of an amine-functionalized graphene oxide surface with organosilane: efficient catalyst for the Knoevenagel condensation of malononitrile with aldehydes at mild temperature

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Abstract

In this study, a series of Pickering emulsions for catalysis of Knoevenagel condensations of malononitrile with aldehydes were prepared by surface modification of amine-functionalized graphene oxide (GO-NH2) with trimethoxymethylsilane (MTMS). The catalytic activity of the prepared Pickering emulsion system in a Knoevenagel condensation was mainly determined by the active sites and properties (namely droplet size, density, and distribution) of the emulsion. The results show that the mass ratio of 3-aminopropyltrimethoxysilane to MTMS affects the active catalytic sites and properties of the Pickering emulsion. Under conditions that provided a large number of active catalytic sites in the Pickering emulsion, modification of the surface of amine-functionalized GO with an organosilane enhanced substrate adsorption on the catalyst and improved the properties of water-in-oil Pickering emulsions. This increased the Picking emulsion catalytic activity. The Pickering emulsion prepared with GO-NH2 : Si = 1.8 : 0.2 gave the highest catalytic activity in a Knoevenagel condensation at 40 °C, and its activity was much higher than that of GO-NH2. The Pickering emulsion with GO-NH2(1.8)–Si(0.2) still showed high catalytic activity after six cycles and therefore has good reusability.

Graphical abstract: Preparation of a Pickering emulsion by modification of an amine-functionalized graphene oxide surface with organosilane: efficient catalyst for the Knoevenagel condensation of malononitrile with aldehydes at mild temperature

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Article information


Submitted
08 Dec 2019
Accepted
11 Mar 2020
First published
12 Mar 2020

New J. Chem., 2020, Advance Article
Article type
Paper

Preparation of a Pickering emulsion by modification of an amine-functionalized graphene oxide surface with organosilane: efficient catalyst for the Knoevenagel condensation of malononitrile with aldehydes at mild temperature

B. Qian, F. Wang, D. Li, Y. Li, B. Zhang and J. Zhu, New J. Chem., 2020, Advance Article , DOI: 10.1039/C9NJ06097A

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