Mesoporous Skeleton Research Articles

One‐Pot Synthesis of Ordered Mesoporous NiSiAl Oxides for Catalyzing CO2 Reforming of CH4

Ordered mesoporous NiSiAl composite oxides with an amorphous phase were prepared by an improved evaporation‐induced self‐assembly strategy. The silica was distributed homogeneously in the mesoporous skeleton and improved the ordered mesoporous structure of NiAl. Catalytic tests toward the CO2 reforming of CH4 indicated that the NiSiAl exhibited higher catalytic activity and stability over 100 h at 700 °C than NiAl. The enhanced performance results from the high thermal stability induced by Si doping, which hinders the Al2O3 phase transformation from amorphous to γ‐Al2O3; therefore, the uniform dispersion of the Ni nanoparticles is retained owing to the confinement effect of the ordered mesopores. The stabilized Ni nanoparticles reinforced the resistance of the catalyst to carbon deposition and, thus, boosted its durability. Notably, even under more stringent conditions (750 °C, 200 h), NiSiAl‐0.10 retained its amorphous Al2O3 structure and showed outstanding durability, almost without any deactivation.

Ordered mesoporous CoO-NiO-Al2O3 bimetallic catalysts with dual confinement effects for CO2 reforming of CH4

Ordered mesoporous CoO-NiO-Al2O3 bimetallic catalysts with different Co/Ni molar ratios were prepared by an evaporation-induced self-assembly method. The samples were characterized by means of XRD, N2 physisorption, H2-TPR, TEM, XPS, Raman and TGA, and tested for CO2 reforming of CH4. Characterization results indicated that the formation of Ni-Co nano-alloy anchored in the ordered mesoporous skeleton led to the enhancement of stability of active sites and thus suppressed carbon deposition during reforming reaction, particularly for the C5N5 catalyst. Compared with the ordered mesoporous monometallic NiO-Al2O3 catalyst, the C5N5 catalyst exhibited superior stability without obvious deactivation for 150h reforming reaction and holds a promising candidate for cost-effective reforming process.

Efficient adsorptive desulfurization by task‐specific porous organic polymers

A task‐specific mesoporous organic polymer (TSPOP) with unique features like good porosity and rich aromatic phenyl groups was facilely made and utilized as a promising adsorptive desulfurization absorbent for the first time. The material exhibits an efficient saturated adsorption of dibenzothiophene (DBT), as high as 111.1 mg g−1. In addition, the intrinsic mesoporous skeleton of TSPOP gave rise to a facile incorporation of uniform Ag(I) species inside the network which facilitated the uptake of organosulfur compounds. A significantly higher saturated DBT adsorption for Ag(I)‐loaded TSPOP reaches 203.7 mg g−1 via a multiple‐site interaction. A detailed model study based on the density functional calculation provides a deeper understanding of the origin of this high activity. In addition to the π–π stacking between DBT and phenyl rings, there exists an additional π‐complexation adsorption with Ag(I) ions, thus, significantly improving the DBT capture performance. © 2016 American Institute of Chemical Engineers AIChE J, 62: 1740–1746, 2016

Implication of mesoporous 3-D graphene skeleton platform based on interconnected framework architecture in constructing electro-conductive flexible nanocomposites

Various polymer nanocomposites exhibiting elecro-conductivity along with flexibility were successfully fabricated by construction of the graphene-based three-dimensional (3-D) mesoporous skeleton platform derived from 3-D interconnected framework architecture constituted with two-dimensional (2-D) graphitic nanosheets, and the subsequent infiltration of polymer into pore volumes of the skeleton platform. The mesoporous 3-D skeleton platform of graphene has been easily constructed by the aggregation of graphene-coated polystyrene (PS) hybrid spheres prepared through ionic interacton between anionic graphene nanosheets and cationic PS nanospheres, and the subsequent thermal removal of polymer components, which made it possible to provide well-made pathways for electron transport as well as empty pores for the following infiltration of polymer matrix component. When a flexible polymer such as PVDF-HFP was chosen as a polymer matrix component entering into pore volumes of the graphene skeleton platform, the graphene/polymer nanocomposite tended to exhibit interesting behavior of electrical conductivity, which is comparable to that of neat graphene skeleton platform, and also maintained the initial value even under half-folding condition, evidencing excellent structural stability of the graphene skeleton. Furthermore, it was found that exchange of polymer matrix does not significantly alter the electrical conductivity of nanocomposite, confirming again the performance of 3-D graphene skeleton employing interconnected framework architecture as electron transport pathway. The ability to embed 3-D graphene skeleton into polymer matrix is a great opportunity to impart high electrical and mechanical properties to polymer composite formulation. Open image in new window

Hierarchically porous titania xerogel monoliths: synthesis, characterization and electrochemical properties

Hierarchically porous titania (TiO2) xerogel monoliths were successfully synthesized by a facile sol–gel process accompanied by phase separation in the presence of formamide (FA) and triblock copolymer F127, followed by ambient pressure drying to remove the solvents. Gelation of the system has been mediated by FA, while F127 enhances a phase-separation. The resultant dried xerogel presents a hierarchically porous structure constructed by large macropores and mesoporous skeletons, which exhibits a high BET surface area of 444m2g−1. Heat-treatment at 800°C results in the formation of the crystalline anatase phase with high thermal stability, without spoiling the macrostructure. The as- prepared porous TiO2 xerogel displays superior electrochemical properties, and the specific capacity of TiO2 xerogel could remain over 114mAhg−1 (69mAhcm−3) at 1C after 100 cycles, representing a good cycling stability.

Faculty acceptance testing of multimedia-based e-learning resources on core competencies for interprofessional collaborative practice

Ordered mesoporous Cu–Mg–Al composite oxides were synthesized via the one-pot evaporation-induced self-assembly strategy. Using this method, copper was first homogeneously incorporated into the ordered mesoporous spinel matrix. After H2 reduction treatment, according to X-ray diffraction (XRD) and transmission electron microscopy (TEM) results, copper existed as metallic nanoparticles with the size of 6–10 nm that well decorated the parent mesoporous skeleton. The metallic nanoparticles were then re-oxidized to copper oxide when exposed to air or during CO oxidation reaction at low temperatures. Thus, copper migrated from bulk spinel phase to the surface after the reduction–oxidation treatment. Moreover, the copper on the surface was re-incorporated into the bulk spinel phase by further thermal treatment at much higher temperature in the presence of air. The correlation between the state of copper in the mesoporous composite oxides and the catalytic performance toward CO oxidation was studied. It was found that copper existed as oxide nanoparticles on the surface of mesoporous Mg–Al skeleton is much more active than that existed as lattice Cu ions in spinel phase.

Effect of reduction–oxidation treatment on structure and catalytic properties of ordered mesoporous Cu–Mg–Al composite oxides

Ordered mesoporous Cu–Mg–Al composite oxides were synthesized via the one-pot evaporation-induced self-assembly strategy. Using this method, copper was first homogeneously incorporated into the ordered mesoporous spinel matrix. After H2 reduction treatment, according to X-ray diffraction (XRD) and transmission electron microscopy (TEM) results, copper existed as metallic nanoparticles with the size of 6–10nm that well decorated the parent mesoporous skeleton. The metallic nanoparticles were then re-oxidized to copper oxide when exposed to air or during CO oxidation reaction at low temperatures. Thus, copper migrated from bulk spinel phase to the surface after the reduction–oxidation treatment. Moreover, the copper on the surface was re-incorporated into the bulk spinel phase by further thermal treatment at much higher temperature in the presence of air. The correlation between the state of copper in the mesoporous composite oxides and the catalytic performance toward CO oxidation was studied. It was found that copper existed as oxide nanoparticles on the surface of mesoporous Mg–Al skeleton is much more active than that existed as lattice Cu ions in spinel phase.

Mesoporous N-doped carbons prepared with thermally removable nanoparticle templates: an efficient electrocatalyst for oxygen reduction reaction.

Thermally removable nanoparticle templates were used for the fabrication of self-supported N-doped mesoporous carbons with a trace amount of Fe (Fe-N/C). Experimentally Fe-N/C was prepared by pyrolysis of poly(2-fluoroaniline) (P2FANI) containing a number of FeO(OH) nanorods that were prepared by a one-pot hydrothermal synthesis and homogeneously distributed within the polymer matrix. The FeO(OH) nanocrystals acted as rigid templates to prevent the collapse of P2FANI during the carbonization process, where a mesoporous skeleton was formed with a medium surface area of about 400 m(2)/g. Subsequent thermal treatments at elevated temperatures led to the decomposition and evaporation of the FeO(OH) nanocrystals and the formation of mesoporous carbons with the surface area markedly enhanced to 934.8 m(2)/g. Electrochemical measurements revealed that the resulting mesoporous carbons exhibited apparent electrocatalytic activity for oxygen reduction reactions (ORR), and the one prepared at 800 °C (Fe-N/C-800) was the best among the series, with a more positive onset potential (+0.98 V vs RHE), higher diffusion-limited current, higher selectivity (number of electron transfer n > 3.95 at +0.75 V vs RHE), much higher stability, and stronger tolerance against methanol crossover than commercial Pt/C catalysts in a 0.1 M KOH solution. The remarkable ORR performance was attributed to the high surface area and sufficient exposure of electrocatalytically active sites that arose primarily from N-doped carbons with minor contributions from Fe-containing species.

Highlights from the latest articles in nano-oncology.

Highlights from the latest articles in nano-oncology.

Mass transport of small retained molecules in polymer-based monolithic columns

The mass transport properties of a non-retained (thiourea) and three retained low molecular weight compounds (acetophenone, valerophenone, and octanophenone) along a 4.6mm×45mm PROSWIFT™ RP-1S monolithic column made of rigid cross-linked poly(styrene-divinylbenzene) copolymer was investigated in depth. Accurate protocols (peak parking experiments, measurement of the first and second central moments of peak profiles by numerical integration) combined with the use of validated models of effective diffusion along monolithic structures were applied for the determination of the longitudinal diffusion, the eddy dispersion, and the skeleton–eluent mass transfer resistances due to the finite analyte diffusivity across the polymer skeleton and to the slow absorption kinetics into the polymer volume. Experimental results show by increasing order of importance evidence that the resolution performance of this short and wide polymer-based monolithic HPLC column is limited by the slow analyte diffusivity across the polymer skeleton (smaller than one tenth of the bulk diffusion coefficient for k′>1), its large eddy dispersion HETP (Heddy≃100μm), and the slow rate of absorption (≃10Hz only) in the polymer volume for retained analytes. The column performance could be improved by preparing a more homogeneous material with a rigid internal mesoporous structure. This would provide a column bed having a larger specific surface area, allowing faster analyte diffusion across the mesoporous skeleton, a smaller eddy dispersion HETP, and a faster absorption kinetics in the polymeric monolith than those observed for the currently available materials.

Experimental and numerical validation of the effective medium theory for the B-term band broadening in 1st and 2nd generation monolithic silica columns

Effective medium theory (EMT) expressions for the B-term band broadening in monolithic silica columns are presented at the whole-column as well as at the mesoporous skeleton level. Given the bi-continuous nature of the monolithic medium, regular as well as inverse formulations of the EMT-expressions have been established. The established expressions were validated by applying them to a set of experimental effective diffusion (Deff)-data obtained via peak parking on a number of 1st and 2nd generation monolithic silica columns, as well as to a set of numerical diffusion simulations in a simplified monolithic column representation (tetrahedral skeleton model) with different external porosities and internal diffusion coefficients. The numerically simulated diffusion data can be very closely represented over a very broad range of zone retention factors (up to k″=80) using the established EMT-expressions, especially when using the inverse variant. The expressions also allow representing the experimentally measured effective diffusion data very closely. The measured Deff/Dmol-values were found to decrease significantly with increasing retention factor, in general going from about Deff/Dmol=0.55 to 0.65 at low k″ (k″≅1.5–3.8) to Deff/Dmol=0.25 at very high k″ (k″≅40–80). These values are significantly larger than observed in fully-porous and core–shell particles. The intra-skeleton diffusion coefficient (Dpz) was typically found to be of the order of Dpz/Dmol=0.4, compared to Dpz/Dmol=0.2–0.35 observed in most particle-based columns. These higher Dpz/Dmol values are the cause of the higher Deff/Dmol values observed. In addition, it also appears that the higher internal diffusion is linked to the higher porosity of the mesoporous skeleton that has a relatively open structure with relatively wide pores. The observed (weak) relation between Dpz/Dmol and the zone retention factor appears to be in good agreement with that predicted when applying the regular variant of the EMT-expression directly to the mesoporous skeleton level.

Improvement of catalytic performance of preferential oxidation of CO in H2-rich gases on three-dimensionally ordered macro- and meso-porous Pt–Au/CeO2 catalysts

Three-dimensionally ordered macro- and meso-porous (3DOM) M/CeO2 (M=Pt, Au and Pt–Au) catalysts supported with different noble metal nanoparticles of Pt, Au and Pt–Au alloy were synthesized by thermal decomposition of cerium nitrate precursor using the close packed structures of PS colloidal crystals as templates. The obtained 3DOM M/CeO2 catalysts possess well-defined 3DOM skeletons composed of ultrafine CeO2 nanoparticles. The macroporous CeO2 skeletons contain the mesoporous walls possessing the nanopores of ∼3–4nm and the noble metal nanoparticles of Pt, Au, and Pt–Au alloy with the grain sizes of ∼5.0nm homogenously dispersed. The catalytic performance of CO preferential oxidation (PROX) in H2-rich gases on 3DOM Pt/CeO2, Au/CeO2, and Pt–Au/CeO2 catalysts were systematically studied. The superior catalytic performance with 90% CO conversion and 83% CO2 selectivity are realized on 3DOM 1wt.% Pt1Au1/CeO2 catalyst at 80°C under the weight hourly space velocity of 30,000mLg−1h−1. Moreover, the 3DOM 1wt.% Pt1Au1/CeO2 catalyst exhibits excellent catalytic stability maintaining 90% CO conversion and 56% CO2 selectivity even after the test period of 260h under the same flow rate. The three-dimensionally ordered macro- and meso-porous skeletons, the synergistic effect due to the formation of Pt–Au alloy, and the strong interaction of Pt–Au alloy nanoparticles with CeO2 supports are identified to be beneficial to the improvement of catalytic activity and stability of CO PROX. The obtained 3DOM Pt–Au/CeO2 catalysts may be potential candidates with the improved catalytic performance of CO PROX reaction in H2-rich gases for polymer electrolyte membrane fuel cells (PEMFCs) applications.

Building self-ordered tubular macro- and mesoporous nitridated titania from gas bubbles towards high-performance lithium-ion batteries

Robust well-defined tubular structural materials based on macro- and mesoporous nitridated titania (TMMN-TiO2) were obtained by a simple solution-phase approach in ammonia solution. In this approach, the gas bubbles derived from ammonia solution play the role of templates that direct the ordered growth in the form of a tubular structure. The results demonstrated that the volume ratio of ammonia to water can be favorable for the formation of TMMN-TiO2, which are characterized by FESEM and FTIR. What is more, ammonia was used not only as the template but also as the nitrogen source. Interestingly, it was found that the TiO2 nanocrystals building blocks were assembled into an interconnected mesoporous skeleton and built in ordered tubular macroporous channels. This unique architecture provides many important features that are required for high-performance anodes, such as fast ion transport, high conductivity, and structure stability, thus enabling an electrode with outstanding lithium storage performance. For example, such an electrode delivers 112 mA h g(-1) capacity at 5100 mA g(-1) (30 C) even after 1200 cycles.

Lysine-aided PMMA-templating preparation and high performance of three-dimensionally ordered macroporous LaMnO3 with mesoporous walls for the catalytic combustion of toluene

Rhombohedrally crystallized three-dimensionally ordered macroporous (3DOM) perovskite-type oxides LaMnO3 with mesoporous skeletons were prepared using the poly(ethylene glycol) (PEG)- and/or l-lysine-assisted poly(methyl methacrylate) (PMMA)-templating method. Physicochemical properties of the materials were characterized by numerous analytical techniques. Catalytic performance of the as-prepared LaMnO3 samples was evaluated for the combustion of toluene. It is found that addition of appropriate amounts of PEG400 and l-lysine was beneficial for the generation of high-quality 3DOM-structured LaMnO3 (denoted as LaMnO3-PL-1, LaMnO3-PL-2, and LaMnO3-PL-3 derived with a PEG400/l-lysine molar ratio of 1.23, 0.61, and 0.31, respectively) with mesoporous skeletons and high surface areas (32–38m2/g). Among the LaMnO3 samples, the LaMnO3-PL-2 one possessed the largest surface area and the highest contents of surface Mn4+ and adsorbed oxygen species. 3DOM-structured LaMnO3 showed better low-temperature reducibility than bulk LaMnO3, with the LaMnO3-PL-2 sample displaying the best low-temperature reducibility. Under the conditions of toluene concentration=1000ppm, toluene/O2 molar ratio=1/400, and space velocity=20,000mL/(gh), the porous LaMnO3 catalysts remarkably outperformed the nonporous bulk counterpart; over the best-performing LaMnO3-PL-2 catalyst, the temperatures required for toluene conversion=50 and 90% were ca. 226 and 249°C, respectively. The apparent activation energies (58–61kJ/mol) for toluene combustion over the LaMnO3-PL-1–3 catalysts were much lower than that (97kJ/mol) over the bulk LaMnO3 catalyst. It is concluded that the large surface area, high oxygen adspecies content, good low-temperature reducibility, and unique bimodal pore structure were responsible for the good performance of 3DOM-architectured LaMnO3 with mesoporous skeletons for toluene combustion.

Inverse opal tungsten trioxide films with mesoporous skeletons: synthesis and photoelectrochemical responses

Inverse opal structured tungsten trioxide (WO(3)) films with mesoporous morphology were prepared using self-assembled polystyrene (PS) colloid as an organic template and by addition of polyethyleneglycol (PEG) to a precursor as an organic surfactant. The photoelectrochemical properties of these films were investigated. By adjusting the tungsten to PEG weight ratio in the precursor, an inverse opaline WO(3) film with a nano-particular skeleton and increased specific surface area was constructed. The unique morphology of this film led to enhanced photoelectrochemical catalytic responses under UV-Visible 1-sun illumination.

Pumping with electroosmosis of the second kind in mesoporous skeletons

This paper presents the use of mesoporous silica skeletons as substrates for electroosmotic (EO) micropumps. Mesoporous silica skeletons have bimodal pore size distributions consisting of macropores and cation-permselective mesopores. These materials have the potential for high flow rate per power because the cation-permselective mesopores can generate an induced charge layer (ICL) and electroosmosis of the second kind (EO-2) under high applied electric fields. The diffuse charge layers induced by the electric field result in an EO-2 flow rate that increases quadratically with increasing electric field. In contrast, the flow rate of the more common electroosmosis of the first kind (EO-1) is linearly proportional to electric field. Here, we investigate the impact of finite pressure loads on the EO-2 flow rate with experiments and an engineering model to evaluate the potential of mesoporous skeletons for micropumping applications. Our results include analyses of maximum flow rate, maximum pressure, and flow rate with intermediate pressure loads. The results indicate the existence of a critical pressure load at which reverse pressure-driven flow significantly diminishes the EO-2 flow. We also investigate the scaling of flow rate per power with respect to substrate thickness and area, demonstrating significant increases in flow rate per power with thinner substrates and favorable scaling for miniaturization of EO-2 pumps.

Ceramic microfluidic monoliths by ice templating

Meso/macro-porous alumina microfluidic monoliths were fabricated by an ice-templating (or freeze-casting) technique. A (green) compact with sufficient strength is obtained after controlled freezing and simple drying under ambient conditions by starting with an aqueous suspension of a mixture of submicrometer-sized α-alumina and nanometer-sized γ-alumina. A monolith with high surface area (30 m 2 g −1) is obtained after sintering at 900 °C. The hierarchical structure of these monoliths consists of slit-shaped macro-pores enclosing a meso-porous skeleton with pore sizes from 20 to 60 nm. The advanced porous structure of the monoliths and their easy preparation suggests large potentials for application as flow-through catalyst support.

Synthesis and characterization of SBA-15 macrospheres with hierarchical pore structure

The new macroscopic-scale SBA-15 spheres with diameter of 0.2–0.5 mm are prepared by a sol–gel method, in which the tetrabutylorthosilicate (TBOS) is used as silicon source and triblock copolymer (P123) and polyoxyethylene octylphenol ether (OP-10) are used as templates. The resulting spherical samples are characterized by XRD, N 2 adsorption–desorption, TEM and SEM methods. The results show that the inner structure of SBA-15 macrospheres has macroporous channels (0.5 μm) and mesoporous skeleton (4–5 nm). These SBA-15 macrospheres with the hierarchical pore structure demonstrate high absorption capacity for Emodin molecules.

Preparation of hierarchical porous carbon by post activation

A series of hierarchical porous carbons (HPCs) have been prepared by a combination of soft-templating and post activation. As evidenced by N 2 sorption tests, the pristine mesopores were basically preserved and micropores were generated on the mesopore wall of mesoporous carbon (MC). The micropore generation on the mesoporous skeleton can be controlled by simply adjusting the KOH ratio and activation temperature. The BET surface area, mesopore surface area and total pore volume of the HPCs increase monotonously with increasing activation temperature and KOH/MC ratio. In contrast, the micropore surface area reaches the maximum at the ratio of KOH/MC of 4. Further increase of KOH/MC ratio and activation temperature reduces the micropore surface area. Structural characterizations confirm that the main mesopore channel was preserved during activation.

Synthesis and dye separation performance of ferromagnetic hierarchical porous carbon

Ferromagnetic hierarchical porous carbon (FHPC) with nickel particles embedded in the hierarchical porous carbon skeleton was synthesized. The hierarchical macro–mesoporous skeleton was formed by dissolving a salt template of Na 2CO 3 and the ferromagnetic nickel particles were produced by in situ carbothermal reduction of nickel oxide. The saturation magnetization, remnant magnetization and coercive force of FHPC are 11.3 emu g −1, 2.3 emu g −1 and 55.7 Oe. The ferromagnetic property enables the magnetic separation of the FHPC from water. The surface chemical environments of the FHPC consist of different oxygen functional groups, like –OH, >COO and >CO groups, as well as a trace amount of aliphatic species of –CH 3 or - CH 2 - structures. Dye separation performance of the FHPC was investigated using methylene orange, and the adsorption capacity was 0.16 mg m −2 with the adsorption kinetics constant of 2.2 m 2 mg −1 min −1, which is superior to that of magnetic carbon spheres.