Uniform Mesopores Research Articles

Elucidating the conformation effects within adsorption of natural organic matter on mesoporous graphitic carbon

The conformation effects were frequently reported to affect the adsorption of natural organic matter (NOM), but such a specific mechanism is poorly understood. To address this knowledge gap, based on the adsorption of NOM on mesoporous graphitic carbon nitride (MCN) prepared via a novel pseudo-templating method, the conformation effects were elucidated. The results showed that MCNs nano-architectures with uniform mesopores were successfully fabricated and showed prominent adsorption capacity. The maximum adsorption amounts of MCN-0.5 for fulvic acid (FA) and leonardite humic acid (HA) were 73.61 mgC g−1 and 135.57 mgC g−1, respectively. The adsorptive affinities of components for HA and Elliott soil HA (ESHA) were related to structural condensation; the components with the more coiled conformation exhibited higher affinities because of occupying less active sites and weakening the electrostatic repulsion. Such conformation effects were further established with respect to NOM types and components, as well as solution chemistry. HA and ESHA suffered from variations from the coiled to linear conformations as pH increased, but not the other four types of NOM tested, and particularly the humic-like and territorial humic-like components were critical in such conformational variations. The adsorption of HA and ESHA was affected by pH via both the conformation effects and the interaction mechanism. By contrast, the conformation of six types of NOM was not affected by the common cations (Na+, K+, Mg2+, Ca2+), and these cations impacted NOM adsorption only through the conventional interactions.

Block copolymer-templated gasochromic WO3 thin films with uniform mesopores for fast optical hydrogen sensing

A method to prepare mesoporous WO3 thin films (represented by MP-WO3) with a uniform pore size of ∼18 nm is developed successfully by utilizing poly(ethylene oxide)-b-polystyrene (PEO-b-PS) as the structure-directing agent (SDA). The properties of the gasochromic MP-WO3 thin film are studied in detail and compared with the control groups prepared by using homopolymer PEO, PS, or their mixtures as SDA. Utilizing an optimized thermal treatment procedure, the gasochromic MP-WO3 thin film of which the transmittance change ΔT is 59.1% exhibites the fastest coloration and bleaching speed with a coloration time of 27.3 s and a bleaching time of 19.7s as well as excellent reversibility within 90 cycles. This study offers a new strategy and insight into the development of mesoporous WO3 hydrogen gasochromic films with excellent performances and paves its way toward the application of an optical hydrogen sensor.

Hierarchical porous nickel tin sulfide nanosheets as a binder free electrode for hybrid supercapacitor

The utilization of free-standing sulfide-based hybrid nanostructures plays a paramount role in supplying the steadily increasing demand for energy storage devices. Herein, this report presents the growth of outstanding binder-free Ni-Sn sulfide thin films for high-performance supercapacitors via the revised successive ionic layer adsorption and reaction (r-SILAR) method. Molar concentration ratios between Ni/Sn have been studied, and the optimum designed mesoporous Nix-Sn1.0xS/Ni foam (NF), a single cathode electrode material, successfully achieved outstanding specific capacitance of 2890 F/g at 5 A/g, capacitance retention of 85 %, and coulombic efficiency of 100 % after 10,000 cycles. Moreover, the constructed Nix-Sn1.0xS/NF//activated carbon (AC) hybrid supercapacitor device delivers an ultrahigh power density of 53.469 KW/Kg and capacitance retention of 95 % with robust long-term cycling stability up to1000 cycles. The superior electrochemical performance of the prepared Nix-Sn1.0xS electrode could be attributed to: (i) the synergistic effect of the two binary metal sulfides (Ni/Sn) into reversible faradaic redox reaction; (ii) the growing mechanism of the ultra-thin film (1.2 nm) as a binder-free electrode, enhance the ions insertion/extraction, and (iii) the formation of hierarchically flower-like architecture with uniform mesopores provides a high surface area (62.2 m2/g) and intensifies active sites for faradaic redox reactions. These encouraging results present a novel avenue for constructing advanced free-standing electrode materials for high-performance supercapacitors.

Synthesis of tetramethylbenzene from CO2 hydrogenation over ZnZrO/ZSM-11 tandem catalyst

The synthesis of aromatics via CO2 hydrogenation is receiving an increasing attention. However, the direct conversion of CO2 to a single aromatic product with high selectivity is very challenging. Herein, we report a synthesis of tetramethylbenzene(TeMB) on a tandem catalyst consisting of ZnZrO and hierarchical ZSM-11 zeolite, the selectivity of TeMB up to 79 % in aromatics is achieved while maintaining 76 % total aromatic selectivity. Uniform mesopores of ZSM-11 created with mixed TPAOH and NaOH organic-inorganic base are found to be responsible for the increased selectivity of aromatics and TeMB. Based on the acidic property of the catalyst, the increase of TeMB selectivity is attributed to the increase in the amount of the external BrØnsted acid which is increased with the external surface area of ZSM-11 zeolite. More BrØnsted acid on the external surface promotes the alkylation of low-carbon aromatics such as xylene, therefore increases the selectivity of TeMB.

Synthesis of Mesoporous Lanthanum-Doped SnO2 Spheres for Sensitive and Selective Detection of the Glutaraldehyde Disinfectant.

Glutaraldehyde disinfectant has been widely applied in aquaculture, farming, and medical treatment. Excessive concentrations of glutaraldehyde in the environment can lead to serious health hazards. Therefore, it is extremely important to develop high-performance glutaraldehyde sensors with low cost, high sensitivity, rapid response, fabulous selectivity, and low limit of detection. Herein, mesoporous lanthanum (La) doped SnO2 spheres with high specific surface area (52-59 m2 g-1), uniform mesopores (with a pore size concentrated at 5.7 nm), and highly crystalline frameworks are designed to fabricate highly sensitive gas sensors toward gaseous glutaraldehyde. The mesoporous lanthanum-doped SnO2 spheres exhibit excellent glutaraldehyde-sensing performance, including high response (13.5@10 ppm), rapid response time (28 s), and extremely low detection limit of 0.16 ppm. The excellent sensing performance is ascribed to the high specific surface area, high contents of chemisorbed oxygen species, and lanthanum doping. DFT calculations suggest that lanthanum doping in the SnO2 lattice can effectively improve the adsorption energy toward glutaraldehyde compared to pure SnO2 materials. Moreover, the fabricated gas sensors can effectively detect commercial glutaraldehyde disinfectants, indicating a potential application in aquaculture, farming, and medical treatment.

The effect of the number of hydrophobic tails of cationic ammonium surfactants on mesoporous TiO2 synthesized

Mesoporous titanium dioxide (TiO2) is one of the most studied mesoporous materials considering its special character and various applications. In the present work, mesoporous TiO2 was synthesized by a sol–gel method employing different hydrophobic tails of ammonium cationic surfactants templates. The prepared samples were characterized by various techniques. The XRD profiles confirmed that all samples crystallized into the TiO2 anatase phase. The crystallite size of all samples was found to vary in the range of 8.60 nm to 13.61 nm. The transition temperature of the anatase phase was increased to several Celsius degrees since TiO2 was fabricated with a template assistant. The surface area of the mesoporous TiO2 was increased in the range of 93 m2.g−1 (CTAB) − 116.8 m2.g−1 (MTAB). These values were larger than the TiO2 synthesized without a template (72 m2.g−1). The total pore volume was also increased between 0.1704 cm3.g−1 (CTAB) and 0.300 cm3.g−1 (MTAB), while the TiO2 synthesized without a template was only 0.161 cm3.g−1. Using CTAB and DDAB yield a uniform mesopore size distribution. MTAB tends to produce non-uniform pore of the mesoporous system. The soft-templating method opens up new possibilities for synthesizing mesoporous metal oxides.

Dual-template induced interfacial assembly of yolk-shell magnetic mesoporous polydopamine vesicles with tunable cavity for enhanced photothermal antibacterial

Yolk-shell magnetic polymer nanostructures with large cavity, movable magnetic core are attractive carriers for bulk storage, release and transport of guest molecules in various applications. However, it remains great challenge to achieve a controllable transport of guest species into and out from the hollow space in a controlled way due to the lack of tailor-made nanostructures. Herein, a dual-template-induced emulsion interfacial assembly and polymerization method (denoted as de-IAP) was developed to constructyolk-shell magnetic mesoporous polydopamine (YS-MMP) vesicles with magnetic core, large hollow space and uniform mesopores in the soft polymer shell. The obtained YS-MMP vesicles possess tunable cavity size (10–900 nm), flexible mesoporous PDA layer, large pores (21 nm), high surface area (217.4 m2·g−1) and high magnetization saturation (31.0 emu·g−1), thus exhibiting the merits of high loading capacity (29.1%) and encapsulation rates (41.0%) of Curcumin (Cur), and fast magnetic separation speed. Thanks to their superior photothermal effect and magnetic property, the obtained YS-MMP@Cur vesicles exhibit smart on-demand release of Cur and excellent recyclability. With 808 nm laser irradiation, YS-MMP@Cur vesicles show high-efficient photothermal bactericidal effect (>99%) against S. aureus and E. coli, opening up a new avenue for smart cargo delivery, lasting sterilization, and environmental remediation.

Engineering S, N-doped carbon nanosheets derived from thiazolothiazole-based conjugated polymer for efficient electrocatalytic oxygen evolution and Zn-air battery

Electrochemical oxygen evolution reaction (OER) and oxygen reduction reaction (ORR) by using metal-free electrocatalysts is an emerging research interest for clean energy due to its cost affordability and eco-friendliness. However, only a few metal-free electrocatalysts are reported to exhibit robust OER and ORR performances, although OER and ORR are very important in various energy technology like metal-air batteries, fuel cells, etc. Herein, we have developed a rigid thiazolo [5,4-d] thiazole-based organic conjugated polymer, P-TzTz, and its polymer-derived N and S-doped carbon nanosheets for metal-free electrocatalytic OER and ORR. The polymer possesses a unique two-dimensional nanosheet structure with a moderate surface area of 72.6 m2/g and a wide range of pore sizes. The synthesized P-TzTz displayed a reasonable electrocatalytic OER performance with excellent long-term stability. The OER performance was further enhanced by pyrolyzing the P-TzTz at 800 °C to prepare the N and S-doped carbon nanosheet, P-TzTz-CNS800. The elevated surface area (228 m2/g) with uniform mesopores, enhanced electrical conductivity of P-TzTz-CNS800, and the presence of N, and S as the dopants for improving active sites made the P-TzTz-CNS800 a promising OER/ORR electrocatalyst as it showed the OER overpotential of 347 mV@10 mA/cm2 current density with more than 45 h long-range durability and 98% Faradic efficiency of oxygen evolution. Finally, to utilize the good OER efficacy of P-TzTz-CNS800-based metal-free electrocatalyst, a rechargeable Zn-air battery was fabricated as a proof of concept by taking P-TzTz-CNS800 as the air cathode. The Zn-air battery revealed a constant open circuit potential of 1.44 V and high charging/discharging stability over 40 h with a minimal loss in round trip frequency. Thus, the report corroborates the promising potential of P-TzTz derived N and S-doped carbon nanosheets as an efficient metal-free electrocatalyst as an air cathode for Zn-air battery for clean energy conversion.

Development of Microdrip Enzyme Device Using Carbon-Coated Porous Silica Spheres

Carbon-coated porous silica spheres (C/PSSs) are particles with uniform particle and mesopore sizes, on which a thin layer of carbon is uniformly deposited on the surface by chemical vapor deposition. The continuous carbon deposit over the mesopore network allows the C/PSS to be electrically conductive and more chemically stable over its traditional counterparts, such as PSS, porous carbons, and carbon electrodes. As homogeneous particles, C/PSS can also be arranged uniformly on an electrode by screen printing to construct macroscopic networks that facilitate the diffusion of substances. Herein, C/PSS was synthesized and fabricated into a working electrode for a prototype glucose enzyme sensor to perform electrochemical measurements on a sample size of 20 μL. We selected the two enzymes, glucose dehydrogenase (GDH) and glucose oxidase (GOD), and water-soluble mediators, quinoline-5,8-dione (QD), to demonstrate the functionality of the sensor. The GDH sensor achieved a linear response up to 75 mM glucose concentration much higher than commercial sensor strips and the GOD sensor up to 25 mM. The results proved that the response current was mainly controlled by glucose diffusion. We succeeded in developing a sensor chip with C/PSS arranged on the surface with high efficiency by selecting a mediator that can smoothly transfer electrons to and from carbon, which enables various sensing applications. This work is the demonstration of the triple pore structure of the C/PSS electrode for enzyme electrode reactions.

Biotemplate-assisted synthesis of CuO hierarchical tubes for highly chemiresistive detection of dimethylamine at room temperature

The fabrication of low-temperature metal oxide-based sensors with highly sensitive to carcinogenic organic-amines remains challenging. Herein, a biomorphic CuO-5 material was synthesized by simply immersing mulberry twig slices in copper nitrate solution and calcining the precursors in air at 500 ℃. Its multistage tubes are assembled from well-crystallized nanoparticles, and possess uniform mesopores and abundant oxygen vacancies. These microstructural factors facilitate the rapid diffusion of gas molecules to sensing layer, and improve the conductivity of CuO material, as well as the content of active sites and surface adsorbed oxygen species. In particular, under the synergy of adsorption and catalysis of the suspended bonds for surface Cu2+ ions, this material achieves the high sensing and selective detection of trace dimethylamine (DMA) at room temperature for the first time. At 25 °C, CuO-5 sensor reaches a response value of 35.9–50 ppm DMA, which is 8.3 times larger than that of template-free CuO-0 sample. Meanwhile, the sensor also has good response-recovery reproducibility, low detection limit, and satisfactory moisture resistance and stability. In addition, the mechanism for enhanced sensing of DMA at room temperature is discussed in detail.

Thin and Uniform Mesoporous TiO2-Wrapped MoO2 Submicrospheres as Anode Materials for Enhanced Electrochemical Performances

MoO2 has great potential for applications in rechargeable batteries, supercapacitors, and catalysis. However, its application for a long duration remains a challenge. Here, an effective strategy is presented to enhance its structural and chemical stability by wrapping a thin layer of porous oxide on MoO2 particles. Mesoporous TiO2-coated MoO2 (MoO2@mTiO2) submicrospheres are thus designed and controllably fabricated via kinetics-controlled coating and thermal treatment. The composite submicrosphere is built of a spherical MoO2 core and a thin amorphous mesoporous TiO2 shell with a tunable thickness, showing the enhanced structural and chemical stability. Their formation is attributed to the NH4+-mediated tiny TiO2 nanoparticle deposition mechanism. Importantly, the MoO2@mTiO2-based electrode for lithium-ion batteries can maintain a high reversible capacity of up to ∼970 mAh g–1 at 1 A g–1 even after 380 cycles, which is much higher than that of the bare MoO2 microsphere-based electrode, exhibiting excellent cycling performance. Further experiments have revealed that there exists an optimal TiO2 shell thickness (about 12 nm), and overly thin or thick TiO2 shells are unfavorable to a long cycling performance with high capacity. In addition, this MoO2@mTiO2 electrode can always maintain a high reversible capacity of above 200 mAh g–1 at 1 A g–1 even after 1000 cycles for sodium-ion batteries, showing a good practical prospect. This study provides not only a facile route for the fabrication of MoO2@mTiO2 submicrospheres but also a potential electrode material with enhanced structural and chemical stability for lithium (or sodium)-ion batteries.

Kinetics‐Controlled Synthesis of Ordered Mesoporous Carbon Single Crystals from Liquefied Wood

AbstractThe architectures of carbon materials prepared via soft‐templating method greatly depend on the assembly pattern of micelles. Herein, a kinetics‐controlled strategy is developed to fabricate ordered mesoporous carbon (OMC) single crystals from liquefied wood by using melamine to regulate the polymerization rate of carbon precursors, which further affects the assembly process. Due to the slow hydroxymethylation reaction of melamine with formaldehyde in acid, the addition of melamine can decelerate the reaction kinetics to produce no seed nuclei at the initial stage, which favors the composite micelles to orderly aggregate and further grow in a layer‐by‐layer pattern to form OMC single crystals after carbonization. The OMC single crystals with high specific surface areas (733 m2 g−1), uniform mesopore size (3.2 nm), and ordered Im3m mesostructure are ideal supports to couple with Ag nanoparticles to act as efficient catalysts, which exhibits remarkable catalytic performance for the reduction of 4‐nitrophenol.

Dual-response drug released hollow materials for the ultrasonic theranostics of acute myocardial infarction

Acute myocardial infarction (AMI) is a type of serious heart attack. Timely diagnosis and treatment of patients greatly improved their survival and prognosis. Unfortunately, during the progression of AMI, some diagnostic markers, including ST-segment elevation on electrocardiograph and serum troponin, sometimes cannot be obtained changing at an early stage. In addition, the imaging methods such as CT cannot dynamically monitor the AMI. Ultrasound (US) imaging can be considered as a convenient and non-invasive medical diagnosis modality in clinical. But it lacks the targeted ultrasound contrast agent for the diagnosis of AMI. High expression of MMP-9 and ROS was found to be happened with AMI. However, a single targeting of one between them could be interfered by other factors. Here, we successfully synthesized the hollow organic material combining the polymerization of MMP-9 substrate polypeptide and ROS responsive organic compounds in order to have more accuracy targeting to AMI. Dimethyldiethoxysilane (DMDES) was used to achieve colloidal stabilized oil-in-water emulsion template. Thus, the polypeptide and ROS-responsive compound, which have the opposite polarity, can be dissolved in water and oil species, respectively, and react on the surface of these two phases. Moreover, the curcumin (CUR) was also loaded into the hollow material for the targeted release, which realized the theranostics. This material was confirmed with uniform particle size, hollow mesopores, biosafety and ultrasonic imaging enhancement ability both in vitro and in vivo. Furthermore, this material was also demonstrated to have MMP-9 and ROS targeting imaging enhancement and drug releasement both in vitro and in vivo, as well as good therapeutic effects on AMI model cells or mice.

A nanocellulose-mediated, multiscale ion-sieving separator with selective Zn2+ channels for durable aqueous zinc-based batteries

A heterostructure engineered, multiscale ion-sieving separator with desired macro‑meso-molecular pores that can render selective Zn2+ permeability and homogeneous Zn2+ distribution at the separator-electrode interface is designed to achieve durable aqueous Zn-ion batteries. The proposed separator is fabricated by stacking an intermediate nanocellulose layer and a poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) upper layer on a glass fiber substrate, wherein the nanocellulose layer contains uniform mesopores favoring a homogeneous Zn2+ flux and endowing the attainment of a PEDOT:PSS layer. While the PEDOT:PSS layer features intrinsic ionic/electronic conductivity and rich sulfonate groups enabling uniform electrical field distribution and inhibiting anions migration. The combination of mesoporous nanocellulose and cation-permeable PEDOT:PSS used in the heterostructure separator yields a high ionic transference number and fast Zn2+ desolvation kinetics. This unique separator enables highly compact and dendrite-free Zn deposition at 4 mA cm−2/8 mAh cm−2, and sustains the symmetric Zn||Zn cell over 400 h at 10 mA cm−2/4 mAh cm−2. Such advantages bring remarkable reversibility to full AZBs with high I2 mass loading cathodes of 13.0 mg cm−2, delivering a discharge capacity of 172.1 mAh g−1 after 1000 cycles. This multiscale ion-sieving design principle provides new insight into separator engineering for ultra-stable Zn metal batteries.

Au-Loaded Superparamagnetic Mesoporous Bimetallic CoFeB Nanovehicles for Sensitive Autoantibody Detection.

Construction of a well-defined mesoporous nanostructure is crucial for applying nonnoble metals in catalysis and biomedicine owing to their highly exposed active sites and accessible surfaces. However, it remains a great challenge to controllably synthesize superparamagnetic CoFe-based mesoporous nanospheres with tunable compositions and exposed large pores, which are sought for immobilization or adsorption of guest molecules for magnetic capture, isolation, preconcentration, and purification. Herein, a facile assembly strategy of a block copolymer was developed to fabricate a mesoporous CoFeB amorphous alloy with abundant metallic Co/Fe atoms, which served as an ideal scaffold for well-dispersed loading of Au nanoparticles (∼3.1 nm) via the galvanic replacement reaction. The prepared Au-CoFeB possessed high saturation magnetization as well as uniform and large open mesopores (∼12.5 nm), which provided ample accessibility to biomolecules, such as nucleic acids, enzymes, proteins, and antibodies. Through this distinctive combination of superparamagnetism (CoFeB) and biofavorability (Au), the resulting Au-CoFeB was employed as a dispersible nanovehicle for the direct capture and isolation of p53 autoantibody from serum samples. Highly sensitive detection of the autoantibody was achieved with a limit of detection of 0.006 U/mL, which was 50 times lower than that of the conventional p53-ELISA kit-based detection system. Our assay is capable of quantifying differential expression patterns for detecting p53 autoantibodies in ovarian cancer patients. This assay provides a rapid, inexpensive, and portable platform with the potential to detect a wide range of clinically relevant protein biomarkers.

Molten Salt-Assisted Construction of Hollow Carbon Spheres with Outer-Order and Inner-Disorder Heterostructure for Ultra-Stable Potassium Ion Storage.

The central goal of high-performance potassium ion storage is to control the function of the anode material via rational structural design. Herein, N- and S-doped hollow carbon spheres with outer-short-range-order and inner-disorder structures are constructed to achieve highly efficient and ultra-stable potassium ion storage using a low-temperature molten salt system. The ultrathin carbon walls and uniform mesoporous as well as unique heterostructure synergistically realize significant potassium storage performance via facilitating rapid diffusion of potassium ions and alleviating substantial volume expansion. Furthermore, as the anode of a potassium ion battery, the as-prepared MSTC electrode demonstrates a state-of-the-art cycling capability of 221.3 mAh g-1 at 1 A g-1 after 20,000 cycles. The assembled potassium ion hybrid capacitor device demonstrates a high energy of 157 Wh kg-1 at 956 W kg-1 and excellent reversibility at a current density of 5.0 A g-1 after 20,000 cycles with 82.7% capacity retention. Accordingly, our work provides new ideas for designing advanced carbon anode materials and understanding the charge storage mechanism in potassium ion battery, as well as constructing high energy-power density potassium-ion hybrid capacitors (PIHCs).

Synthesis of aminated three-layered hollow mesoporous organosilica spheres and in-situ loading gold nanoparticles

• atHMOSs with amino groups were synthesized by a sol-gel method and a subsequent hydrothermal treatment procedure. • The prepared atHMOSs exhibited well-defined three-layered hollow structure and uniform mesopores. • The amino group in atHMOS gives it the ability to load large amounts of gold nanoparticles. Hollow mesoporous spheres with hierarchical structure and functional groups were considerably interest in separation, catalysis, and biomedicine. In this work, aminated three-layered hollow mesoporous organosilica spheres (atHMOSs) are synthesized for the first time by successively co-assembling multiple organosilanes with surfactant and a subsequent hydrothermal treatment procedure. Electron microscopy shows that the prepared atHMOSs have a well-defined three-layered hollow structure with a monodisperse diameter (440 nm) and a uniform mesopores (4.1 nm). Importantly, owing to the doped amino groups successfully, the atHMOSs can effectively coordinate with gold ions, and thus gold nanoparticles loaded in atHMOSs are further prepared after reducing the adsorbed gold ions.

Ordered Mesopore Confined Pt Nanoclusters Enable Unusual Self-Enhancing Catalysis.

As an important kind of emerging heterogeneous catalyst for sustainable chemical processes, supported metal cluster (SMC) catalysts have received great attention for their outstanding activity; however, the easy aggregation of metal clusters due to their migration along the substrate's surface usually deteriorates their activity and even causes catalyst failure during cycling. Herein, stable Pt nanoclusters (NCs, ∼1.06 nm) are homogeneously confined in the uniform spherical mesopores of mesoporous titania (mpTiO2) by the interaction between Pt NCs and metal oxide pore walls made of polycrystalline anatase TiO2. The obtained Pt-mpTiO2 exhibits excellent stability with well-retained CO conversion (∼95.0%) and Pt NCs (∼1.20 nm) in the long term water-gas shift (WGS) reaction. More importantly, the Pt-mpTiO2 displays an unusual increasing activity during the cyclic catalyzing WGS reaction, which was found to stem from the in situ generation of interfacial active sites (Ti3+-Ov-Ptδ+) by the reduction effect of spillover hydrogen generated at the stably supported Pt NCs. The Pt-mpTiO2 catalysts also show superior performance toward the selective hydrogenation of furfural to 2-methylfuran. This work discloses an efficient and robust Pt-mpTiO2 catalyst and systematically elucidates the mechanism underlying its unique catalytic activity, which helps to design stable SMC catalysts with self-enhancing interfacial activity in sustainable heterogeneous catalysis.

Phosphotungstic acid-promoted Mn-Fe bimetal oxide with high sulfur resistance for low-temperature selective catalytic reduction of nitrogen oxides with NH3

The catalysts with low-temperature activity and high sulfur resistance are expected in the denitration application. To obtain an efficient and eco-friendly catalyst for NOx abatement, phosphotungstic acid (HPW) promoted Mn-Fe bimetal oxide composites were constructed by colloidal solution combustion synthesis followed by the impregnation method. Their catalytic mechanism and activity at low temperature analyzed in detail by XRD, BET, SEM, XPS, H2-TPR, NH3-TPD and in situ DRIFTS characterizations. The results show that the large surface area and uniform mesoporous of Mn-Fe oxide contributed to the dispersion of HPW nanoparticles. The highly dispersed HPW can regulate the surface acidity and redox property of the catalyst. The Mn0.25Fe0.75-HPW50 compound combined the redox property of mesoporous Mn-Fe oxide and the acidic advantage of HPW showed a wider operating temperature window (125–400 °C, NOx conversion >94%) with higher N2 selectivity and SO2 resistance. Langmuir-Hinshelwood (L-H) and Eley-Rideal mechanisms (E-R) coexist in the SCR reaction. This work can provide a strategy for designing composite materials with low-temperature activity and high sulfur resistance. The developed porous HPW-promoted Mn-Fe oxide would be a promising catalyst candidate for NOx removal.

Homomesoporous Metal-Organic Framework for High-Performance Electrochromatographic Separation.

Metal-organic frameworks (MOFs) have exhibited tremendous potential in the area of separation science. However, most of the developed MOF-based stationary phases contained only microporous structures and suffer from limited separation performance. Herein, homomesoporous MOFs with excellent mass transfer capability and strong thermodynamic interactions are first explored as the novel stationary phase for high-performance capillary electrochromatographic separations. As a proof of concept, noninterpenetrated mesoMOF-1 with uniform mesopore sizes (22.5 × 26.1 Å) and good stability was facilely grown on the inner surface of capillaries and applied as a homomesoporous MOF coating-based stationary phase for high-efficiency electrochromatographic separation. Seven types of analytes with different molecular dimensions were all baseline separated on a mesoMOF-1 coated column with high theoretical plate numbers and excellent repeatability, exhibiting significantly improved separation selectivity and column efficiency in comparison to a microporous HKUST-1 coated column. The maximum column efficiencies of the mesoMOF-1 coated column for substituted benzenes and halobenzenes reached up to 1.4 × 105 plates/m, and its mass loadability was also much higher than that of the HKUST-1 coated column. In addition, based on the analysis of adsorption kinetics and chromatographic retention behaviors, the interaction and retention mechanisms of different molecular-weight analytes on mesoMOF-1 coated stationary phases were systematically explored and disclosed in detail. These results indicate that the homomesoporous MOF-based stationary phase can effectively balance the kinetic diffusion (mass transfer capability) and thermodynamic interactions (the strength of adsorption interaction), having great potential for high-performance chromatographic separation.