Poly(ethylene glycol) stabilized mesoporous metal-organic framework nanocrystals: efficient and durable catalysts for the oxidation of benzyl alcohol.

Active, selective, and stable: The fabrication of uniform mesoporous Cu3(BTC)2 (BTC: 1,3,5-benzenetricarboxylate) nanocrystals with tunable size and porosity is reported. The as-synthesized Cu3(BTC)2 structures show high activity, selectivity, and stability for the aerobic oxidation of benzyl alcohol to aldehyde.

Switching micellization of pluronics in water by CO2.

The micellization of amphiphilic molecules is an interesting topic from both theoretical and practical points of view. Herein we have studied the effects of compressed CO(2) on the micellization of Pluronics in water by means of fluorescence, UV/Vis spectra, and small-angle X-ray scattering. It was found that CO(2) can induce the micellization of Pluronics in water, and the micelle can return to the initial state of molecular dispersion after depressurization. Therefore, the micellization of Pluronics in water can be switched through the easy control of pressure. Different from the common micelles with hydrophobic cores, interestingly, this CO(2)-induced micelle has an amphiphilic core, in which hydrophobic and hydrophilic domains coexist. On account of the ability to dissolve both polar and nonpolar components in the micellar core, the CO(2)-induced micelles can improve the reagent compatibilities frequently encountered in various applications. In an attempt to address this advantage, this micelle was utilized as template to the one-step synthesis of Au/silica core-shell composite nanoparticles. Furthermore, the underlying mechanism for the CO(2)-induced micellization of Pluronics in water was investigated by a series of experiments.

Water-in-oil-in-water double nanoemulsion induced by CO(2).

The cetyltrimethylammonium bromide (CTAB)/water/heptane emulsion system with different CO(2) pressure has been studied. The phase behavior investigation shows the nanoemulsion can be formed at suitable pressure range. The generalized indirect Fourier transformation (GIFT) analysis of the small-angle X-ray scattering (SAXS) data has drawn a clear picture of the structural information of the nanoemulsion, which reveals that the droplet of emulsion has a double structure with both the outer and inner droplet size in nanometre range. Furthermore, the investigation of the heptane/CTAB/water/CO(2) emulsion system by using electrical conductivity confirms the emulsion type transforms from O/W to W/O/W. In addition, the effect of different CTAB concentration on the nanoemulsion formation has been studied. It is found that enough CTAB concentration is necessary for the inclusion of continuous water into oil droplets. We also explored the application of the W/O/W double nanoemulsion in material synthesis. Interestingly, the hollow silica spheres with double shells were obtained in this CO(2)-induced double nanoemulsion.

Carbon dioxide in ionic liquid microemulsions.

Tailor-made emulsion: a CO(2) -in-ionic-liquid microemulsion was produced for the first time. The CO(2)-swollen micelles are "tunable" because the micellar size can be easily adjusted by changing the pressure of CO(2). The microemulsion has potential applications in materials synthesis, chemical reactions, and extraction.

Cylindrical-to-spherical shape transformation of lecithin reverse micelles induced by CO2.

The effect of CO(2) on the microstructure of L-alpha-phosphatidylcholine (lecithin) reverse micelles was studied. The small-angle X-ray scattering (SAXS) results show that CO(2) could induce a cylindrical-to-spherical micellar shape transformation. Fourier transform infrared (FT-IR) and UV-vis techniques were also utilized to investigate intermolecular interactions and micropolarity in the reverse micelles at different CO(2) pressures. The reduction of the degree of hydrogen bonding between surfactant headgroups and water with added CO(2) was found to be the main reason for the micellar shape transformation. In the absence of CO(2), the hydrogen bonding between water and P=O of lecithin forms a linking bridge in the interfacial layer. Therefore, the free movement of the polar head of lecithin is limited and the cylindrical reverse micelles are formed. Upon adding CO(2) to the reverse micelles, the hydrogen bonds between lecithin and water in reverse micelles are destroyed, which is favorable to forming spherical micelles. Moreover, the CO(2)-combined reverse micelles were utilized in the synthesis of silica particles. Rodlike silica nanoparticles were obtained in the absence of CO(2), and ellipsoidal and spherical mesoporous silica particles were formed in the presence of CO(2). This method of tuning micellar shape has many advantages compared to traditional methods.

Hollow metal-organic framework polyhedra synthesized by a CO2-ionic liquid interfacial templating route.

We proposed for the first time a CO2-ionic liquid (IL) interfacial templating route for the production of hollow MOF microparticles. By adding the gaseous CO2 into IL phase under stirring, a large number of CO2 bubbles are generated, which provide numerous CO2-IL interfaces, serving as the nucleation or agglomeration centers for the MOF nanocrystals. By this strategy, the hollow and mesoporous Zn-BTC (BTC: 1,3,5-benzenetricarboxylic) tetrahedroids were fabricated. The morphologies of the Zn-BTC polyhedra can be easily controlled by CO2 pressure. The as-synthesized Zn-BTC hollow microparticles have shown potential applications in gas separation and catalysis. Furthermore, the CO2-IL interface templating approach has been successfully applied to the fabrication of microsized Zn-BDC (BDC: 1,4-benzenedicarboxylic) hollow prisms.

Large-pore mesoporous Mn3O4 crystals derived from metal-organic frameworks.

The large-pore mesoporous Mn3O4 crystals with tunable morphologies, size and porosities were synthesized via the conversion of metal-organic frameworks, which were fabricated by utilizing the nanostructural organizations of ionic liquid-water mixtures as templates. Mn3O4 showed high catalytic activity for the degradation of methyl blue in the wastewater treatment.

Ionic liquid-in-ionic liquid nanoemulsions.

A new type of nanoemulsion formed by two immiscible ionic liquids was prepared for the first time. This novel kind of emulsion involves no volatile organic solvent. Metal-organic framework nanorods with large mesopores were synthesized in the nanoemulsion.

High-internal-ionic liquid-phase emulsions.

High-internal-ionic liquid-phase emulsions were formed for the first time. The novel emulsions are very stable and do not involve any volatile organic solvent. They have great potential of applications in different fields, such as material synthesis, extraction, encapsulation, and chemical reactions.

Formation of multiple water-in-ionic liquid-in-water emulsions.

Emulsions composed of an ionic liquid (IL) 3-methyl-1-octylimidazolium hexafluorophosphate, water, and surfactant TX-100 (poly(ethylene glycol)-tert-octylphenyl) were studied by laser confocal scanning microscopy, stability determination and electrical conductivity. Multiple water-in-ionic liquid-in-water (W/IL/W) emulsions were formed around water volume fractions ~0.70. Further studies showed that the W/IL/W multiple emulsions were formed through an inversion between water-in-IL emulsion and IL-in-water emulsion.

Surfactant-directed assembly of mesoporous metal-organic framework nanoplates in ionic liquids.

Mesoporous MOF nanoplates were formed in surfactant-IL solutions. This method is simple, requires less energy, and is environmental friendly, and can be easily applied to the synthesis of other MOFs with different morphologies and porosities.

CO2 capture by hydrocarbon surfactant liquids.

Here we found that CO(2) has high solubility in low-cost hydrocarbon surfactant liquids.

Efficient separation of surfactant and organic solvent by CO2.

CO(2) can be used to separate surfactant and organic solvent completely in various surfactant/solvent solutions without contaminating the surfactants and solvents. We believe that the simple, efficient, and greener method has wide applications.