New Monolithic Capillary Columns with Well-Defined Macropores Based on Poly(styrene-<i>co</i>-divinylbenzene)

Macroporous polymer monoliths based on poly­(styrene-<i>co</i>-divinylbenzene) with varied styrene/divinylbenzene ratios have been prepared by organotellurium-mediated living radical polymerization. The well-defined cocontinuous macroporous structure can be obtained by polymerization-induced spinodal decomposition, and the pore structures are controlled by adjusting the starting composition. The separation efficiency of small molecules (alkylbenzenes) in the obtained monoliths has been evaluated in the capillary format by high-performance liquid chromatography (HPLC) under the isocratic reversed-phase mode. Baseline separations of these molecules with a low pressure drop (∼2 MPa) have been achieved because of the well-defined macropores and to the less-heterogeneous cross-linked networks

Ultralow-Density, Transparent, Superamphiphobic Boehmite Nanofiber Aerogels and Their Alumina Derivatives

Ultralow-Density, Transparent, Superamphiphobic Boehmite Nanofiber Aerogels and Their Alumina Derivative

Ultralow-Density, Transparent, Superamphiphobic Boehmite Nanofiber Aerogels and Their Alumina Derivatives

Ultralow-Density, Transparent, Superamphiphobic Boehmite Nanofiber Aerogels and Their Alumina Derivative

Synthesis, Reduction, and Electrical Properties of Macroporous Monolithic Mayenite Electrides with High Porosity

Room-temperature stable macroporous mayenite electride (C12A7:e^–) has been successfully prepared via a sol–gel method accompanied by phase separation, followed by heat-treatment and reduction processes. The obtained xerogel monoliths possess controllable macrostructure and a porosity of more than 60%, depending on adjusting the amount of poly­(ethylene oxide) as a phase separation inducer. Heat-treatment allows the formation of multicrystals Ca₁₂Al₁₄O₃₂Cl₂ and Ca₁₂Al₁₄O₃₃ (C12A7), and the porosity increases to 78.67% after being heat-treated at 1100 °C. Further reduction promotes the transformation from Ca₁₂Al₁₄O₃₂Cl₂ or C12A7 to C12A7:e^– as well as the conversion from an insulator to a semiconductive electride. The carrier concentration of the electride reaches 3.029 × 10¹⁸ cm^–3 after being reduced at 1100 °C under Ar atmosphere, and the porosity still remains 66%. The macrostructure of the resultant mayenite electride before and after heat-treatment and reduction is perfectly preserved, indicating that the obtained macroporous monolithic mayenite electride could be utilized in the electronic components

Synthesis, Reduction, and Electrical Properties of Macroporous Monolithic Mayenite Electrides with High Porosity

Room-temperature stable macroporous mayenite electride (C12A7:e^–) has been successfully prepared via a sol–gel method accompanied by phase separation, followed by heat-treatment and reduction processes. The obtained xerogel monoliths possess controllable macrostructure and a porosity of more than 60%, depending on adjusting the amount of poly­(ethylene oxide) as a phase separation inducer. Heat-treatment allows the formation of multicrystals Ca₁₂Al₁₄O₃₂Cl₂ and Ca₁₂Al₁₄O₃₃ (C12A7), and the porosity increases to 78.67% after being heat-treated at 1100 °C. Further reduction promotes the transformation from Ca₁₂Al₁₄O₃₂Cl₂ or C12A7 to C12A7:e^– as well as the conversion from an insulator to a semiconductive electride. The carrier concentration of the electride reaches 3.029 × 10¹⁸ cm^–3 after being reduced at 1100 °C under Ar atmosphere, and the porosity still remains 66%. The macrostructure of the resultant mayenite electride before and after heat-treatment and reduction is perfectly preserved, indicating that the obtained macroporous monolithic mayenite electride could be utilized in the electronic components

Hierarchically Porous Carbon Monoliths Comprising Ordered Mesoporous Nanorod Assemblies for High-Voltage Aqueous Supercapacitors

This report demonstrates a facile one-pot synthesis of hierarchically porous resorcinol-formaldehyde (RF) gels comprising mesoporous nanorod assemblies with two-dimensional (2D) hexagonal ordering by combining a supramolecular self-assembly strategy in the nanometer scale and phase separation in the micrometer scale. The tailored multilevel pore system in the polymer scaffolds can be preserved through carbonization and thermal activation, yielding the multimodal porous carbon and activated carbon (AC) monoliths. The thin columnar macroframeworks are beneficial for electrode materials due to the short mass diffusion length through small pores (micro- and mesopores). By employing the nanostructured AC monolith as a binder-free electrode for supercapacitors, we have also explored the capability of “water-in-salt” electrolytes, aiming at high-voltage aqueous supercapacitors. Despite that the carbon electrode surface is supposed to be covered with salt-derived decomposition products that hinder the water reduction, the effective surface area contributing to electric double-layer capacitance in 5 M bis­(trifluoromethane sulfonyl)­imide (LiTFSI) is found to be comparable to that in a conventional neutral aqueous electrolyte. The expanded stability potential window of the superconcentrated electrolyte allows for a 2.4 V-class aqueous AC/AC symmetric supercapacitor with good cycle performance

Boehmite Nanofiber–Polymethylsilsesquioxane Core–Shell Porous Monoliths for a Thermal Insulator under Low Vacuum Conditions

Boehmite Nanofiber–Polymethylsilsesquioxane Core–Shell Porous Monoliths for a Thermal Insulator under Low Vacuum Condition

Selective Preparation of Macroporous Monoliths of Conductive Titanium Oxides Ti_<i>n</i>O_{2<i>n</i>–1} (<i>n</i> = 2, 3, 4, 6)

Monolithic conductive titanium oxides Ti_<i>n</i>O_{2<i>n</i>–1} (<i>n</i> = 2, 3, 4, 6) with well-defined macropores have been successfully prepared as a single phase, via reduction of a macroporous TiO₂ precursor monolith using zirconium getter. Despite substantial removal of oxide ions, all the reduced monoliths retain the macropore properties of the precursor, i.e., uniform pore size distribution and pore volume. Furthermore, compared to commercial porous Ebonex (shaped conductive Ti_<i>n</i>O_{2<i>n</i>–1}), the bulk densities (1.8 g cm^–3) are half, and the porosities (60%) are about 3 times higher. The obtained Ti_<i>n</i>O_{2<i>n</i>–1} (<i>n</i> = 2, 3, 4, 6) macroporous monoliths could find applications as electrodes for many electrochemical reactions

Recyclable Functionalization of Silica with Alcohols via Dehydrogenative Addition on Hydrogen Silsesquioxane

Synthesis of class II hybrid silica materials requires the formation of covalent linkage between organic moieties and inorganic frameworks. The requirement that organosilylating agents be present to provide the organic part limits the synthesis of functional inorganic oxides, however, due to the water sensitivity and challenges concerning purification of the silylating agents. Synthesis of hybrid materials with stable molecules such as simple alcohols, rather than with these difficult silylating agents, may therefore provide a path to unprecedented functionality. Herein, we report the novel functionalization of silica with organic alcohols for the first time. Instead of using hydrolyzable organosilylating agents, we used stable organic alcohols with a Zn­(II) catalyst to modify the surface of a recently discovered highly reactive macro-mesoporous hydrogen silsesquioxane (HSQ, HSiO_1.5) monolith, which was then treated with water with the catalyst to form surface-functionalized silica. These materials were comprehensively characterized with FT-IR, Raman, solid-state NMR, fluorescence spectroscopy, thermal analysis, elemental analysis, scanning electron microscopy, and nitrogen adsorption–desorption measurements. The results obtained from these measurements reveal facile immobilization of organic moieties by dehydrogenative addition onto surface silane (Si–H) at room temperature with high loading and good tolerance of functional groups. The organic moieties can also be retrieved from the monoliths for recycling and reuse, which enables cost-effective and ecological use of the introduced catalytic/reactive surface functionality. Preservation of the reactivity of as-immobilized organic alcohols has been confirmed, moreover, by successfully performing copper-catalyzed azide–alkyne cycloaddition (CuAAC) “click” reactions on the immobilized silica surfaces

Aerogels from Chloromethyltrimethoxysilane and Their Functionalizations

Reactions of chloromethyltrimethoxysilane (CMTMS) and its derived colloidal network polychloromethylsilsesquioxane (PCMSQ) have been investigated to extend the material design strategy toward functionalized and mechanically reinforced aerogels. In a carefully designed sol–gel system, CMTMS has afforded transparent aerogels in the presence of cationic surfactant. The surface chloromethyl groups with polarity and reactivity are shown to be useful for supporting nanostructures, with photoluminescent carbon dots (C-dots) prepared from polyethylenimine and citric acid as an example. Furthermore, since nucleophilic substitution (S_N2) reactions on the surface chloromethyl groups are found to control the equilibrium of formation/dissociation of siloxane bonds, a new gelation strategy triggered by S_N2 reactions in sol–gel has been developed. In the presence of nucleophilic organic species such as polyamines, a hybrid network consisting of PCMSQ cross-linked with a polyamine nucleophile can be prepared to enhance mechanical properties of aerogel