Metal-Nanoparticles-Loaded Ultrathin g-C₃N₄ Nanosheets at Liquid–Liquid Interfaces for Enhanced Biphasic Catalysis

Abstract

Exploiting new interface-active solid catalysts is crucial to construct efficient Pickering emulsion systems for biphasic catalysis. In this work, ultrathin g-C3N4 nanosheets (g-C3N4-NSs) were developed as a new solid emulsifier to directly position catalytic sites at oil–water interfaces for improving the reaction efficiency of a biphasic reaction. Exemplified by a metal-involved biphasic reaction of nitroarenes reduction, the developed Pd/g-C3N4-NSs catalyst with Pd nanoparticles loaded on the surface of g-C3N4-NSs exhibited excellent activity with a catalytic efficiency of 1220 h–1. Such activity was 4.2 and 17.9 times higher than those of Pd/g-C3N4-bulk and the ordinary Pd/C8-SiO2 catalyst, respectively. Also, in the biphasic oxidation reaction of alcohols, Pd/g-C3N4-NSs achieved a 2.3-fold activity enhancement. It was found by analyzing the solidified emulsion droplets that the Pd/g-C3N4-NSs catalyst was parallelly assembled at the oil–water interfaces. Because of the ultrathin thickness of g-C3N4-NSs, such a unique interfacial assembly behavior allowed precise positioning of Pd nanoparticles at the oil–water interfaces. As a result, the oil-soluble reactant could directly react with the water-soluble reactant at the oil–water interface hosting the Pd nanoparticles. Our elaborately designed reaction interface was believed to substantially avoid the diffusion barrier between oil-soluble and water-soluble reactants and then to significantly enhance the reactivity of biphasic reactions. This work highlights the importance of the interfacial location of catalytic sites in biphasic catalysis.

Tensile Strain in Tin Oxide Clusters Stabilized by C3N4 for Highly Efficient Visible Light-Driven H2O2 Production

“…Owing to the high surface to volume ratio, adjustable size and structure, rich surface chemistry, and adjustable visible light absorption, the nanoscale metal oxide clusters have emerged as promising cophotocatalysts in the photocatalytic field, which has greatly boosted the advancement of many photocatalytic applications, such as water splitting, nitrogen fixation, organic pollutants degradation, and organic synthesis. − Compared to the corresponding nanoparticles, the cluster structure has fascinating photocatalytic activity due to the inherent structure and enhanced quantum size effect. − Herein, we prepared tin oxide (SnO 2 ) clusters modified g-C 3 N 4 (SnO 2 @g-C 3 N 4 ) for a high-efficient photocatalytic hydrogen peroxide generation reaction. The SnO 2 @g-C 3 N 4 is obtained by introducing acetic acid tin (C 8 H 12 O 8 Sn) in the calcination process of urea.…”

Boosting Catalytic Selectivity through a Precise Spatial Control of Catalysts at Pickering Droplet Interfaces

“…Pickering emulsions that are stabilized by solid particles have been documented to be an ideal platform for the assembly of catalysts at oil–water interfaces because of the extremely high stability of the formed droplets. − Up to date, various solid catalysts, including differently shaped SiO 2 , , zeolites, , TiO 2 , and g-C 3 N 4 , , have been reported to be assembled at droplet interfaces for biphasic catalysis. Although enhanced reaction activity has been achieved, these solid catalysts were distributed randomly around the oil–water interfaces, with the one part of active components protruding into the oil phase and the other part into the water phase.…”

Compartmentalized Aqueous-in-Aqueous Droplets for Flow Biocatalysis

“…The most common compartments are formed by droplets, where one liquid is compartmentalized by another immiscible liquid to form numerous dispersed droplets, leading to a high interfacial area between droplet and continuous phases. − For reactions with oil-soluble reagents and products, these aqueous-in-organic emulsion droplets are highly efficient for continuous flow catalysis. , Droplets with catalysts are segmented and clustered into a column . An oil-soluble reagent in the continuous phase makes contact with the catalysts inside the droplet and reacts, generating oil-soluble products that separate and flow with the continuous phase .…”