Dual-templating Approach Research Articles

Dual-Templated Cobalt Oxide for Photochemical Water Oxidation.

Mesoporous Co3 O4 was prepared using a dual templating approach whereby mesopores inside SiO2 nanospheres, as well as the void spaces between the nanospheres, were used as templates. The effect of calcination temperature on the crystallinity, morphology, and textural parameters of the Co3 O4 replica was investigated. The catalytic activity of Co3 O4 for photochemical water oxidation in a [Ru(bpy)3 ](2+) [S2 O8 ](2-) system was evaluated. The Co3 O4 replica calcined at the lowest temperature (150 °C) exhibited the best performance as a result of the unique nanostructure and high surface area arising from the dual templating. The performance of Co3 O4 with highest surface area was further examined in electrochemical water oxidation. Superior activity over high temperature counterpart and decent stability was observed. Furthermore, CoO with identical morphology was prepared from Co3 O4 using an ethanol reduction method and a higher turnover-frequency number for photochemical water oxidation was obtained.

Hierarchically Ordered Porous Carbon as a Host Material for Energetic Composites

Hierarchically ordered macro-/mesoporous carbon (HOPC) was synthesized via a dual-template approach and used as the host matrixes to design the host-guest energetic composites. Monodisperse silica colloidal crystals were used as a hard template, amphiphilic triblock copolymer Pluronic F127 as a soft template, and soluble resols as a carbon source. The obtained HOPC is composed of highly ordered fcc macropores (225 nm), interconnected macropore windows (40 nm), and large mesopores (11.6 nm), resulting in high surface area (503.6 m2/g) and large pore volume (0.833 cm3/g). A high energy material (CL-20) had been encapsulated in HOPC by impregnation process, and the maximum loading amount was around 63 wt.%. The synthesized CL-20/HOPC host-guest energetic composites exhibit much lower thermal decomposition temperature than that of pure CL-20 and their physical mixture.

Fabrication of ordered mesoporous carbons anchored with MnO nanoparticles through dual-templating approach for supercapacitors

Ordered mesoporous carbons anchored with MnO nanoparticles (Cs–Mn) for supercapacitor have been produced by a simple double-template strategy. Pluronic F127 and polyurethane (PU) foam are used as the soft and hard template, respectively, and phenolic resol as a carbon source, and the MnO nanoparticles were in-situ anchored by directly dissolved solid Mn(CH3COO)2⋅2H2O in the phenolic resol solution through evaporation induced self-assembly (EISA) of the mesostructure on the struts of the PU foam scaffold, followed by carbonization. The microstructure, morphology and electrochemical performance of Cs–Mn were investigated by small angle X-ray scattering, transmission electron microscopy, Raman spectropy, nitrogen adsorption–desorption and electrochemical measurements. Results show that Cs–Mn have a hexagonally ordered mesostructure. The pore size of Cs–Mn centered at ca. 2.0–4.2nm, high specific surface area (222m2/g) and great pore volume (up to 0.14cm3/g). The electrochemical measurements show that the Cs–Mn as an electrical double-layer capacitor electrode presents high specific capacitance of 100F/g at a current density of 0.125A/g and excellent rate capability using 0.5M Na2SO4 aqueous solution.

Tunable hierarchical porous silica materials using hydrothermal sedimentation-aggregation technique

Herein, a simple and efficient synthesis based on a dual templating approach allow the preparation of tunable macroporous mesoporous silica materials. Macropores incorporation has been obtained using polymer spheres of well-defined size and their subsequent removal by thermal treatment allowed the independent control of the macropore size entrance between 200 nm and 50 nm. The addition of the block copolymer drives the formation of a second mesostructured skeleton, with a pore size centered around 4 nm, throughout the material framework. By a fine tuning of the sol–gel synthesis parameters (Polymer:TEOS ratio, aging conditions), we succeeded in guiding the SBA-15 rod-like morphology having randomly packed macropores to a derived SBA-15 with a homogeneous honeycomb macrostructure. Moreover, large mesoporous windows are generated between adjacent macropores. Hence, this simple one-pot synthesis approach, allowing scaling-up, offers fine tuning porosity at the macropore scale.

Enhanced electrocatalytic activity of platinum nanoparticles supported on nitrogen-modified mesoporous carbons for methanol electrooxidation

Nitrogen-modified mesoporous carbons (N-MCs) are synthesized via a modified dual-templating approach, in which phenolic polymer is used as a carbon source, dicyandiamide as a nitrogen source, silica nanospheres as a hard template, and triblock copolymer F127 as a soft template, respectively. Structural characterizations reveal that the N-MCs with large mesopore and uniform mesoporous networks possess three different nitrogen-containing groups, all of which can serve as catalytically active sites. Platinum nanoparticles supported on N-MCs (Pt/N-MCs) are prepared by polyol reduction method. As supported by transmission electron microscopy (TEM), homogeneously dispersed Pt nanoparticles are attached to the pore wall of N-MCs with an average size of ca. 2.0 nm, much smaller than that of commercial Pt/C. Electrochemical studies reveal that the Pt/N-MCs has higher electrocatalytic activities for methanol oxidation in comparison to the Pt/MCs and commercial Pt/C, which may be attributed to pyridinic and pyrrolic nitrogen offering p electrons to the sp2 hybridized graphitic carbon layers, leading to the decrease of inner electrical resistance and enhanced proton diffusion rate, as well as a more uniform particle size distribution of Pt on N-MCs.

Preparation of silica nanoflakes with spherical mesopores using a dual-templating approach

A pair of chiral low-molecular-weight amphiphiles (LMWAs) was synthesized from phenylglycine, which forms a viscous solution in water. Mesoporous silica nanoflakes were prepared via a dual-templating approach using F127 block copolymer and the LMWAs. The morphologies and pore architectures of the silica nanoflakes were studied using transmission electron microscopy, field-emission scanning electron microscopy, powder X-ray diffraction, and N2 sorptions. The spherical mesopores opened onto the surfaces of the nanoflakes and were organized in a two-dimensional, hexagonal-like structure. We believe that the pore architectures and morphologies were controlled by the F127 block copolymer and the self-assembly of the LMWAs, respectively. This kind of material has potential for applications in separation and catalysis.

One-step synthesis of three-dimensionally ordered macro–mesoporous silica–alumina composites

In this work, three-dimensional (3D) ordered macro–mesoporous silica–alumina composites were synthesized for the first time in an acid solution, using an effective dual-templating approach. The material with a high surface (i.e., 509m2g−1) possesses spherical macropores with an ordered mesopore structure wall. The strong diffraction peak and the pore size distribution curves reveal the presence of relatively uniform mesopores (3.5nm pore width). The synthesized aluminosilicate materials with tailorable macro–mesoporous structure hold promise in select applications as catalysts, catalyst supports, or adsorbents. This synthesis method also has the potential to make other macro–mesoporous composites with different compositions.

Synthesis of Helical and Supplementary Chirally Doped PMO Materials. Suitable Catalysts for Asymmetric Synthesis

Exciting helical mesoporous organosilicas including supplementary chirally doped moieties into their spiral walls were one-pot successfully synthesized with good structural order for, to the best of our knowledge, the first time. This one-step direct synthesis of helical chirally doped periodic mesoporous organosilica (PMO) materials was carried out by combination of a tartrate-based bis-organosilicon precursor with tetraethyl orthosilicate (TEOS) and two surfactants, cetyltrimethylammonium bromide and perfluoroctanoic acid (CTAB and PFOA). For comparison purposes, a conventional two-step postsynthetic grafting methodology was carried out. In this method, the chiral tartrate-based moieties were grafted onto the helical silica mesoporous materials previously prepared by the dual-templating approach (CTAB and PFOA). The chirally doped materials prepared by both methodologies exhibited helical structure and high BET surface area, pore size distributions, and total pore volume in the range of mesopores. Solid-state (13)C and (29)Si MAS NMR experiments confirmed the presence of the chiral organic precursor in the silica wall covalently bonded to silicon atoms. Nevertheless, one-pot direct synthesis led to a greater control of surface properties and presented larger incorporation of organic species compared with the two-step postsynthetic methodology. To further prove the potential feasibility of these materials in enantiomeric applications, Mannich diastereoselective asymmetric synthesis was chosen as catalytic test. In the case of the one-pot PMO material, the rigidity of the chiral ligand backbone provided by its integration into the inorganic helical wall in combination with the steric impediments supplied by the twisted geometry led to the reagents to adopt specific orientations. These geometrical constrictions resulted in an outstanding diastereomeric induction toward the preferred enantiomer.

Carbonaceous multiscale-cellular foams as novel electrodes for stable, efficient lithium–sulfur batteries

Porous carbon foams were prepared by pyrolysis of a phenolic resin by a dual template approach using silica monoliths as hard templates and triblock copolymers as soft templating agents.

Formation of silica multilamellar vesicles through dual-templating

Silica multilamellar vesicles were prepared with a dual-templating approach using cetyltrimethylammonium bromide (CTAB) and 2-(perfluoro-n-octyl)ethanol (PFOE). The number of layers of the lamellar mesopores increased with increasing PFOE/CTAB molar ratio from 0.2:1 to 0.7:1. When the PFOE/CTAB molar ratios were 0.2:1 and 0.4:1, worm-like pore channels were identified near the outer surfaces, and shrunk lamellar silica shells were identified near the inner surfaces, of the shells of the vesicles. The formation of the mesopores was studied by taking TEM images after different reaction times. It was found that the multilamellar vesicles served as the templates for the lamellar mesopores and the “nucleation” sites for growing silica/surfactant micelles.

Manipulation of mesoporous silica hollow spheres by control of silica precursors

Mesoporous hollow nanospheres have attracted much attention due to their potential applications in the fields of catalysis and drug release. Recently, various hollow silica nanospheres with mesopores in the walls have been prepared through templating approaches. However, the effect of silica precursors on the hollow structure has not been well studied. Herein, mesoporous silica hollow nanospheres were prepared through a chiral amphiphile/organic solvent dual-templating approach. The silica nanostructures are controllable by manipulating the amount of the silica precursors. A diffusion–polycondensation mechanism was proposed to drive the formation of the hollow spheres.

Synthesis of three-dimensionally ordered macro-/mesoporous Pt with high electrocatalytic activity by a dual-templating approach

Three dimensionally ordered macro-/mesoporous (3DOM/m) Pt catalysts are fabricated by chemical reduction employing a dual-templating synthesis approach combining both colloidal crystal (opal) templating (hard-templating) and lyotropic liquid crystal templating (soft-templating) techniques. The macropore walls of the prepared 3DOM/m Pt exhibit a uniform mesoporous structure composed of polycrystalline Pt nanoparticles. Both the size of the mesopores and Pt nanocrystallites are in the range of 3–5 nm. The 3DOM/m Pt catalyst shows a larger electrochemically active surface area (ECSA), and higher catalytic activity as well as better poisoning tolerance for methanol oxidation reaction (MOR) than the commercial Pt black catalyst.

Fabrication of Fe-coordinated diamino-functionalized SBA-15 with hierarchical porosity for phosphate removal

Hierarchically macroporous–mesoporous SBA-15 phosphate adsorbent was synthesized via a dual-templating approach, followed by diamino-functionalization and Fe(III) impregnation. The resulting Fe(III)-coordinated diamino-functionalized macroporous–mesoporous adsorbent possessed well-defined and interconnecting macroporous and mesoporous networks. Its maximum adsorption was 12.7mg/g, which was 86.8% greater than that of Fe(III)-coordinated amino-functionalized mesoporous SBA-15. In the kinetic study of macroporous–mesoporous adsorbent, 92.5% of the final adsorption capacity reached in the first 1min; and the adsorption followed the pseudo-second-order equation well, suggesting the presence of chemisorption. The pH ranging from 3.0 to 6.0 favored the high phosphate adsorption of hierarchically porous adsorbent; however, the coexistence of other anions, especially F−, retarded the adsorption.

Preparation of Chiral Mesoporous Silica Nanotubes and Nanoribbons Using a Dual-Templating Approach

Single-handed helical silica nanotubes and nanoribbons have attracted much attention, due to their potential for applications in asymmetric catalysis and enantioseparation. However, their surface areas are usually lower than 200 m2/g. Herein, single-handed coiled silica nanoribbons with mesopores in their walls were prepared by changing the molar ratio of the chiral low-molecular-weight amphiphiles (LMWAs) and the F127 triblock copolymer, using a dual-templating approach. The obtained samples were characterized using field-emission scanning electron microscopy, transmission electron microscopy, N2 sorption measurements, and X-ray diffraction. The BET surface area reached 700 m2/g. The pore diameters did not change significantly at different LMWA/F127 triblock copolymer molar ratios. The formation of the coiled mesoporous silica nanoribbons was studied by taking TEM images at different times during the reaction. The results indicated that the morphology and the mesopores were controlled by the chiral LMWAs...

3D ordered macro–mesoporous indium doped Al2O3

Three-dimensional ordered macro–mesoporous (3DOMM) Al2O3 and In doped Al2O3 have been successfully synthesized via a dual-templating approach with a colloidal crystal template and surfactant block copolymers. The samples were characterized using X-ray diffraction (XRD), N2 adsorption–desorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), UV-visible (UV-vis) and photoluminescence (PL) spectroscopy. The results indicate that the indium dopants are dispersed well within the mesoporous framework, and the incorporation of indium could efficiently promote the optical properties of the composite. The as-synthesized 3DOMM structures have a large surface area (>200 m2 g−1), and the luminescence intensity of 3DOMM In doped Al2O3 with an In/Al molar ratio of 7% (3DOMM 7In–MAl) is two times higher than that of 3DOMM Al2O3 (3DOMM MAl). Further theoretical calculations, based on first-principle density functional theory (DFT), demonstrate that In doping facilitates the formation of oxygen vacancies, and the hybridization of oxygen vacancy defect states and In 5s, 5p states induce some hybrid states below the conduction band edge. The blue shift of absorption edges of 3DOMM 7In–MAl compared to pure 3DOMM MAl could be attributed to the electron transfer from oxygen vacancies to In atoms.

Flower-like mesoporous silica: a bifunctionalized catalyst for rhodium-catalyzed asymmetric transfer hydrogenation of aromatic ketones in aqueous medium

Functionalized flower-like mesoporous silica with a chiral organorhodium functionality incorporated within its silica framework is prepared through an assembly of chiral 4-((trimethoxysilyl)ethyl)phenylsulfonyl-1,2-diphenylethylenediamine and tetraethoxysilane under a cooperative dual-template approach followed by complexation with organorhodium complexes. Structural characterization discloses its mesostructure and well-defined single-site chiral organorhodium functionality, while electron microscopy analyses reveal the uniformly distributed three-dimensional spherical flowers constructed by the stacking of leaf-shaped nanoflakes. In particular, as a bifunctionalized heterogeneous catalyst, it shows excellent catalytic activity and high enantioselectivity in the asymmetric transfer hydrogenation of aromatic ketones in aqueous medium (more than 99% conversion and up to 97% ee). The superior catalytic performance is attributed to the synergistic effect of the salient cetyltrimethylammonium bromide phase-transfer function and confined chiral organorhodium catalytic nature. Furthermore, this heterogeneous catalyst could be recovered easily and reused repeatedly (ten times) without affecting its ee value, showing a practical application in asymmetric synthesis.

Bio-inspired high performance electrochemical supercapacitors based on conducting polymer modified coral-like monolithic carbon

Inspired by the structure and function of coral in nature, a series of composite electrode materials were prepared via depositing conducting polymers, such as polyaniline (PANi), polythiophene (PTh) and polypyrrole (PPY), on the surface of monolithic coral-like porous carbon (MC). MC with a specific surface area as high as 1125 m2 g−1 was prepared by a facile dual-templating approach. A thin layer of the conducting polymer was formed on the carbon surface. The constitutive properties including the morphology, pore size and specific area were investigated by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Brunauer–Emmett–Teller measurement (BET), respectively. The electrocapacitive properties of electrode materials were evaluated using cyclic voltammetry and galvanostatic charge–discharge cycling in a three electrode system. Compared with MC, the specific capacitances of composite materials had an obvious shift, which reached 1488 F g−1 at a high current density (1.0 A g−1) in an aqueous H2SO4 electrolyte. The coral-like hierarchical porous structure of the carbon favoured the diffusion of the electrolyte ions, hence not only improving the energy storage capacity but also enhancing the power density. The energy density reached 49.5 W h kg−1, even when the maximum power density was 12 000 W kg−1. In addition, such a composite electrode material also showed considerable electrochemical stability, with at least 76.7% of the capacitance being retained after 1000 cycles.

Mesoporous Metallic Cells: Design of Uniformly Sized Hollow Mesoporous Pt–Ru Particles with Tunable Shell Thicknesses

A new class of hollow mesoporous Pt-Ru and Pt particles with uniform size, named 'mesoporous metallic cells', are synthesized through a dual-templating approach using colloidal silica particles and non-ionic surfactants. To realize the full potential of mesoporous metals as electrocatalysts, the shell thicknesses, compositions, and hollow cavity sizes are precisely controlled.

Preparation of frustule-like 1,2-ethylene-silica nanospheres through a chiral amphiphile/organic solvent dual-templating approach

Hollow silica nanospheres with mesopores in the walls have been widely studied because of their potential applications in catalysis and drug release. Hollow organosilica nanospheres also attracted much attention because of their tunable wall backbones and wider applications. Herein, frustule-like 1,2-ethylene-silicas were obtained using a chiral amphiphile, CHCl3, and a dual-templating approach. The morphologies and pore architectures of the 1,2-ethylene-silicas are tunable by changing the amount of CHCl3 in the reaction mixture. With the addition of CHCl3 in the reaction mixtures, hollow 1,2-ethylene-silica nanospheres with opened mesopores in the walls were feasible. Moreover, 1,2-ethylene-silicas with mesopores on the surfaces and coiled pore channels within the walls were obtained using the chiral amphiphile in a single-templating approach. These 1,2-ethylene-silicas were characterized using field-emission scanning electron microscopy, transmission electron microscopy, X-ray diffraction and N2 sorptions.

Macroporous TiO2 foam with mesoporous walls

We demonstrate a simple route for the preparation of new three-dimensionally interconnected hierarchically porous anatase TiO2 foams via a dual-templating approach. The macropores in TiO2 foams are induced through a process of sintering the polyurethane foams template, while a surfactant templating agent promotes the formation of mesopores in the walls of a macroporous monolith of TiO2 foam. The macropore sizes of interconnected networks can be tuned by varying the pores per linear inch of polyurethane foams. This single step method of synthesis from cheap commercially available chemicals is suitable for mass production of three-dimensionally interconnected macro/mesoporous TiO2 foams.