Pickering emulsion prepared by bi-functional graphene oxide as efficient catalyst for aqueous nucleophilic substitution reactions

Abstract

In this contribution, Pickering emulsion system was prepared by bi-functional graphene oxide (GO) grafted with polyethylene glycol (PEG) and 3-aminopropyltrimethoxysilane (APS), which was used as highly efficient catalyst in place of phase transfer catalyst for aqueous nucleophilic substitution reactions. In this Pickering emulsion system, PEG and APS acted as double active sites, in which APS as Lewis base was firstly demonstrated to have catalytic activity for the aqueous nucleophilic substitution. It is found that Pickering emulsion catalytic system prepared by bi-functional GO has more dense droplets distribution and smaller droplets size compared to that by GO-PEG or GO-APS. It can be inferred that APS as stabilizer of oil in water emulsion and PEG showed good synergy for aqueous nucleophilic substitution reactions. It was found that the properties of Pickering emulsion, including droplets distribution and size, was closely related to catalytic performance for the reactions. As the results, Pickering emulsion system in the optimized reaction conditions could exhibit excellent catalytic performance (yield ≥90%) for the production of iodooctane from bromooctane and NaI without stirring. What's more, the spent Pickering emulsion could be easily reconstructed and show good reusability (yiled ≈80%) even after using for seven times.