Ionic liquid-functionalized amphiphilic Janus nanosheets afford highly accessible interface for asymmetric catalysis in water

Phosphotungstate-Functionalized Mesoporous Janus Silica Nanosheets for Reaction-Controlled Pickering Interfacial Catalysis

“…Similar to pristine mesosilica nanosheets, JNS-PW 0.033 exhibits the typical IV-type curves with an H3-type hysteresis loop in its sorption isotherm (Figure 5B vs 5A), which is the characteristic of mesoporous nanosheets. 19,50 This result demonstrates that the mesoporous structure of mesosilica nanosheets is well-kept after incorporating ammonium PW. Actually, we notice that JNS-PW 0.033 shows a similar pore size (3.81 nm) to pristine mesosilica nanosheets (3.80 nm) (Figure 5B, inset vs 5A, inset).…”

“…It not only ensures the sufficient interfacial contact between catalytic species and reactants but also enforces the cooperativity between catalytic sites for a higher reaction rate and selectivity. 56 The produced benzaldehyde was sufficiently shielded in the oil droplets, which prevented the undesired overoxidation to benzoic acid with H 2 O 2 in water, 19 while the produced H 2 O will diffuse out of the oil droplets through the mesopores on JNS-PW x , which further enhances the biphasic oxidation. For these reasons, it is undoubted that the uniform UNS-PW 0.033 , which gave only kinetically stable Pickering emulsions, 55 was far less-efficient Although underwent similar PIC, the selective oxidation of benzyl alcohol with H 2 O 2 showed different reactivities, depending on the droplet sizes of formed Pickering emulsions.…”

“…18,20 Highspeed centrifugation (>18,000 rpm) or filtration is often required to overcome the energy barrier for JNS separation, which inevitably leads to more energy consumption if operated in a large volume. 18,19,21 Therefore, it is a key challenge to strike the balance between long-term stability and rapid demulsification of an emulsion in PIC.…”

“…Oil/water biphasic catalysis has attracted great interest in laboratory synthesis and industrial fabrication, since it is a sustainable platform for producing various important chemicals via organic transformations, enzymatic reactions, and so on. − However, they often suffer from low catalytic efficiency because of the huge mass transfer resistance at a limited oil/water interfacial area. , Pickering interfacial catalysis (PIC) has recently aroused increasing interest for the oil/water biphasic catalysis. In these systems, the solid nanoparticle (NP) acts both as an emulsifier and a interfacial catalyst at the oil/water interface, which provides a large reaction interfacial area for mass transport, hence enhancing catalytic efficiency. − Amphiphilic Janus nanosheets (JNSs) with two opposite wetting surfaces have proven to be excellent candidates for stabilizing Pickering emulsions in PIC, owing to their high aspect ratio, large adsorption energy, and, especially, highly confined rotation at interfaces. − If one side of the JNSs is modified by catalytic sites, the catalytic JNSs will behave as a solid emulsifier and an interfacial catalyst simultaneously, significantly accelerating oil/water biphasic catalysis through the formation of thermodynamically stable Pickering emulsions. − Unfortunately, recovery of JNSs is a tedious process in the thermodynamically stable Pickering emulsions, since the energy moving JNSs from the oil/water interface is much higher than their thermal energy. , High-speed centrifugation (>18,000 rpm) or filtration is often required to overcome the energy barrier for JNS separation, which inevitably leads to more energy consumption if operated in a large volume. ,, Therefore, it is a key challenge to strike the balance between long-term stability and rapid demulsification of an emulsion in PIC.…”

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

“…Since solid catalysts were reported as emulsifiers by Resasco’s group to construct a Pickering emulsion system for biphasic catalysis, numerous nanomaterials such as mesoporous silica, − microporous zeolites, , titanium oxide, and nanoporous carbons , have been explored to stabilize Pickering emulsion for biphasic catalysis. However, when these particles are assembled at the emulsion interfaces, as shown in Scheme a, most of the surface-loaded catalytic sites are protruded partly in the oil phase and partly in the water phase.…”