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The nanoplasmonic metal-driven photocatalytic activity depends heavily on the spacing between metal nanoparticles (NPs) and semiconductors, and this work shows that ethylene glycol (EG) is an ideal candidate for interface spacer. Controlling the synthetic systems at pH 3, the composite of Ag NPs with EG-stabilized amorphous TiO2(Ag/TiO2-3) was synthesized by the facile light-induced reduction. It is verified that EG spacers can set up suitable geometric arrangement in the composite: the twin hydroxyls act as stabilizers to bind Ag NPs and TiO2together and the nonconductive alkyl chains consisting only of two CH2are able to separate the two building blocks completely and also provide the shortest channels for an efficient transfer of radiation energies to reach TiO2. Employed as photocatalysts in hydrogen evolution under visible light, amorphous TiO2hardly exhibits the catalytic activity due to high defect density, whereas Ag/TiO2-3 represents a remarkably high catalytic efficiency. The enhancement mechanism of the reaction rate is proposed by the analysis of the compositional, structural, and optical properties from a series of Ag/TiO2composites.

In recent years, metal–organic frameworks (MOFs) have been explored as emulsifiers for the fabrication of Pickering emulsions and then used for hybrid material synthesis and interface catalysis. Nevertheless, stimuli-responsive Pickering emulsions stabilized by MOFs have been rarely reported so far, although they are of great importance for fundamental research studies and practical applications. Herein, for the first time, triethylenetetramine (TETA)-functionalized MOFs (ZIF-90/TETA) have been designed, synthesized, and used for fabricating CO2-/N2-response Pickering emulsions. It is shown that even at the ZIF-90/TETA content of 0.25 wt %, the functional MOF can still efficiently emulsify n-hexane and water to form a high internal phase Pickering emulsion. Importantly, the Pickering emulsion can be easily and reversibly switched between emulsification and demulsification by bubbling of CO2and N2alternatively at atmospheric pressure. The possible mechanism of the CO2/N2switchable emulsion is investigated by zeta potential, water contact angle, interfacial tension, 13C NMR spectroscopy, and an optical microscope. It is found that the acid–base reaction of CO2with TETA anchored on the surface of ZIF-90 leads to the production of hydrophilic ammonium bicarbonate and carbamate, which results in the emulsification of the Pickering emulsion. However, when N2is bubbled to remove CO2, the reverse reaction takes place to cause the demulsification of the Pickering emulsion. Moreover, the CO2/N2switchable Pickering emulsion has been successfully used as a microreactor for Knoevenagel reactions to demonstrate a highly efficient integration of chemical reaction, product separation, and ZIF-90/TETA recycling for a sustainable chemical process.