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

Abstract

Pickering interfacial catalysis enables oil/water biphasic reactions to efficiently proceed by the formation of stable Pickering emulsions. However, a convenient approach to control the emulsion properties, so as to combine the reactivity and recovery of catalytic emulsifiers, remains challenging to date. Herein, we have reported the switchable transition between emulsification/demulsification controlled by the catalytic reaction process, to realize reaction-controlled Pickering interfacial catalysis. A novel series of phosphotungstate (PW)-functionalized mesoporous Janus silica nanosheets were thus prepared by selectively decorating ammonium PW on one side of mesosilica nanosheets. Characterization results suggested their H2O2-switched reversible emulsification/demulsification behavior in an oil/water biphasic system due to H2O2-induced wettability change in the ammonium PW moiety. The resultant H2O2-switchable Pickering emulsions induced an efficient Pickering interfacial catalysis approach for selective oxidation of alcohols by aqueous H2O2 in water, thus leading to remarkable high conversion and selectivity over a wide range of alcohols. When H2O2 was used up, they could be demulsified spontaneously, resulting in the complete separation of catalytic emulsifiers for steady reuse. The reaction-controlled emulsification/demulsification approach provided a sustainable way to combine reactivity and recovery of catalytic emulsifiers in Pickering interfacial catalysis, which was a benefit for energy-saving in industrial applications.

Inorganic material-based Janus nanosheets: asymmetrically functionalized 2D-inorganic nanomaterials

“…56 This result indicates that Janus nanosheets promote catalytic reactions more efficiently when the interfaces are stabilized. Such silica-based Janus nanosheets with functions as an emulsifier and a catalyst were reported in other studies [57][58][59][60][61] and they exhibited higher efficiency in catalytic reactions than other catalysts without Janus structures. There has been very limited application of Janus nanosheets as a filler for self-healing hydrogels.…”

“…There are a large number of reports about silica-based Janus nanosheets in addition to those mentioned above. Also, various applications for silica-based Janus nanosheets such as surfactants, 43–52 catalysts 53–61 and materials for polymer blends 62–65 have been investigated. The most common application is utilization as surfactants.…”

“…various applications for silica-based Janus nanosheets such as surfactants, [43][44][45][46][47][48][49][50][51][52] catalysts [53][54][55][56][57][58][59][60][61] and materials for polymer blends [62][63][64][65] have been investigated. The most common application is utilization as surfactants.…”

Task‐Specific Janus Materials in Heterogeneous Catalysis

“…The selective oxidation of alcohols to aldehydes and ketones with H 2 O 2 instead of oxygen was also investigated by designing a Pickering interfacial catalytic system containing a phosphotungstate‐functionalized mesoporous Janus material. [45] This solid catalyst was prepared by protonation of surface‐bound aminopropyl groups with different amounts of phosphotungstic acid (H 3 PW 12 O 40 ). The immobilized Janus catalyst showed higher activity and selectivity than H 3 PW 12 O 40 in a homogeneous system.…”

Facile Fabrication of Single-Layer Janus Membrane for Underwater Bubble Unidirectional Transport

“…Membrane technology plays a significant role in modern separation technology and energy applications [1][2][3][4][5]. Particularly in the application of functional membrane with special wettability in oil-water separation [6][7][8][9], fog collection [10,11], wastewater treatment [12,13], catalytic contactor [14,15], osmosis energy harvesting [16][17][18], aeration [19], and so on [20][21][22][23]. Janus membranes are a typical example, which exhibit asymmetric wettability, achieving manipulate liquid wetting and transport behavior by the aid of regulating the gas/liquid/solid multiphase interface [24,25].…”