Targeted Development of Sustainable Green Catalysts for Oxidation of Alcohols via Tungstate-Decorated Multifunctional Amphiphilic Carbon Quantum Dots.

Abstract

Achieving green and sustainable chemical processes by replacing organic solvents with water has always been one of the green chemistry goals and a challenging topic for chemists. However, the poor solubility of organic materials is a major limitation to achieving this goal, especially in alcohol oxidation. In this contribution, the development and design of amphiphilic catalysts via abundant, safe, cheaper, and more biocompatible sources have received notable attention. To this purpose, herein, our group successfully synthesized a new multifunctional amphiphilic carbon quantum dot (CQD) composed of 1-aminopropyl-3-methyl-imidazolium chloride ([APMim][Cl]), dodecylamine (DDA), and citric acid (CA) (denoted as CQDs@DDA-IL/Cl) using a one-pot hydrothermal route. The CQDs@DDA-IL/Cl was then utilized as an amphiphilic stabilizer for anchoring tungsten ions using an anion-exchange method (marked as CQDs@DDA-IL/W). The CQDs@DDA-IL/W as a reusable catalyst selectivity mediated the oxidation of alcoholic substrates with stoichiometric H2O2 in water solvent. The extraordinary performance of our catalyst was attributable to the coexistence of ionic liquid (IL) and DDA upon the surface of the CQDs@DDA-IL/W, which plays a main duty in the hydrophobic/hydrophilic balance, and significantly increase the catalyst compatibility in the aqueous medium with the purpose of removing organic solvents. As a result, the great mass transfer occurs in the two-phase medium using this amphiphilic nanocatalyst without any phase transfer catalyst (PTC) or other additives. The 100% selectivity, excellent turnover number (TON) and turnover frequency (TOF), high yield, almost complete and fast conversion of alcohol to the desired aldehydes and ketones without more oxidation, and easy and no-trouble isolation of product and catalyst are outstanding features of this catalytic system.