Microporous Channels Research Articles

Microwave-assisted synthesis of bimetallic NiCo-MOF-74 with enhanced open metal site for efficient CO2 capture

Metal–organic frameworks (MOFs) containing two different inorganic metal nodes (known as bimetallic MOFs) could exhibit enhanced CO2 adsorption compared to their monometallic counterparts. Herein, a series of bimetallic NiCo-MOF-74 synthesized by microwave-assisted method were investigated for CO2 adsorption. It was revealed that narrow micropore channel with open metal site (OMS) of the bimetallic NiCo-MOF-74 influence CO2 binding affinity and CO2/N2 adsorption. The CO2 uptake of Ni1Co1-MOF-74 at 0 ​°C and 1 ​bar (100 ​kPa) was 8.30 ​mmol ​g−1 which is higher than those of Ni-MOF-74 (3.99 ​mmol ​g−1), Ni6Co1-MOF-74 (3.62 ​mmol ​g−1), Ni1Co6-MOF-74 (6.40 ​mmol ​g−1) and Co-MOF-74 (5.03 ​mmol ​g−1). While this could be related to the high specific surface area of Ni1Co1-MOF-74, Ni1CO2-MOF-74 with relatively low specific surface areas still shows good CO2 adsorption capacity up to 5.70 ​mmol/g, which is higher than those of adsorbents Ni-MOF-74, Ni6Co1-MOF-74 and Co-MOF-74, indicating that adsorption performance mainly relies on coordinated metals. Ni1Co1-MOF-74 showed remarkable recyclability performance, ranking selectivity of CO2/N2 reach up to 34, and suitable isosteric heat (31–23 ​kJ ​mol−1), manifesting a great probability for industrial CO2 capture. As revealed, incorporated Ni2+/Co2+ nodes within Ni1Co1-MOF-74, which are acting as active and open sites for CO2 capture, led to the synergetic effects comprising of micropores as well as dense dual-metal sites.

Direct three-dimensional printed egg white hydrogel wound dressing promotes wound healing with hitching adipose stem cells.

Current wound dressing based on hydrogel offers a promising way to accelerate the healing process, yet great challenges remain in the development of a highly integrated and efficient platform with the combination of therapeutic biomolecules and stem cells. Herein, a natural hydrogel wound dressing from egg white can be conveniently obtained by feasible physical crosslinking, the prepared hydrogel dressing features interconnected microporous channels, direct 3D printing, cytocompatibility, and intrinsic biomolecules to advance cell behavior. The 3D printed egg white hydrogels promote the adhesion and proliferation of adipose-derived stem cells (ASCs) without obvious cytotoxicity. In addition, this integrated hydrogel platform accompanied with adipose-derived stem cells accelerates wound healing through the enhancement of fibroblast proliferation, angiogenesis, and collagen rearrangement in the wound bed. The egg white hydrogel provides an effective wound caring product possessing low cost, easy availability along with ready manufacturing, and advanced therapeutic effect, which may be extended for the management of chronic or other complicated wounds.

Tribological Behaviors and Friction-Induced Vibration and Noise Performance of TC4 with Microporous Channels Filled by Sn-Ag-Cu and Nb2C

Tribological Behaviors and Friction-Induced Vibration and Noise Performance of TC4 with Microporous Channels Filled by Sn-Ag-Cu and Nb2C

Defect-Guided Synthesis of Hierarchical Sn-B-Beta Zeolite with Highly Exposed Sn Sites.

Selectively anchoring active centers on the external surface for forming highly exposed acid sites is a highly desirable but challenging task in zeolite catalyst synthesis. Herein, a defect-guided etching-regrowth strategy is rationally designed for facilely positioning Sn Lewis acid sites on the outer surface of the Sn-B-Beta while fabricating a bifunctional hierarchical structure. The synthesis was conducted by hydrothermal treatment of the as-made B-Beta (uncalcined), which has intrinsic defects of the BEA structure, with Sn source and basic organic structure directing agent (SDA). Under a moderate SDA concentration, with blocked micropore channels, such SDA-triggered etching-regrowth will proceed along the defect defined pathway, which ensures Sn selectively anchored on the external surface. Moreover, this methodology has exclusively introduced tetrahedrally coordinated framework Sn with open Sn sites as the predominated species. Mono- and disaccharide isomerizations in ethanol over different Sn-Beta catalysts proved the prominent advantages of the hierarchical structure with highly exposed and synergetic acid sites.

New Investigation of Asymmetric Wall Temperature and Fluid-Wall Interaction on Radiative Steady MHD Fully Developed Natural Convection in Vertical Micro-Porous–Channel

New Investigation of Asymmetric Wall Temperature and Fluid-Wall Interaction on Radiative Steady MHD Fully Developed Natural Convection in Vertical Micro-Porous–Channel

Bifunctional metal–organic frameworks afforded by postsynthetic modification for efficient cycloaddition of CO2 and epoxides

AbstractBifunctional ionic metal–organic frameworks (MOFs) containing Lewis acid sites (unsaturated metal sites) and halide ions (Cl−, Br−, and I−) have attracted increasing attention due to their extra high activity for the cycloaddition of CO2 with epoxides. Herein, a novel microporous MOF (1‐Eu), namely, [Eu3(L)2(HCOO)(H2O)5]·14H2O (H4L = 2,6‐di(2,4‐dicarboxyphenyl)‐4‐(pyridine‐4‐yl)pyridine), has been synthesized by using a new bipyridyl‐based tetracarboxylate ligands (H4L). Structural analyses show that 1‐Eu is a 3D framework in which 1D chains with alternating triple and single carboxylate bridges are interlinked by the L ligands and contains microporous channels with uncoordinated pyridyl N atoms, which are easy to be modified by N‐methylation. Therefore, three bifunctional N‐methylation 1‐Eu MOFs, 1‐Eu‐MeX (X = Cl−, Br−, and I−), were successfully prepared from the 1‐Eu MOF by a postsynthetic modification (PSM) method. 1‐Eu‐MeX can efficiently catalyze the cycloaddition reaction without any cocatalyst and solvent. Among them, the 1‐Eu‐MeI catalyst displays the highest catalytic performance. Our work thus represents a rare demonstration of ionic MOFs as heterogeneous catalysts for efficient CO2 fixation with epoxides. More significantly, 1‐Eu‐MeX are the first reported Eu‐based ionic MOFs with the bipyridyl‐based tetracarboxylate ligand.

Newly designed microporous organic-inorganic hybrid cobalt phosphonate for hydrogen evolution reaction

The electrochemical water splitting through hydrogen evolution reaction (HER) is a promising technique for generating clean hydrogen as alternative energy to fossil fuel. In recent times, various kinds of cobalt-based materials have been synthesized for hydrogen evolution reactions due to their good catalytic activity, robust structure and stability. New microporous organic-inorganic hybrid cobalt phosphonate material (CoGLy) was developed by a hydrothermal reaction pathway without any structure-directing agent. The material has been characterized through important tools such as powder X-ray diffraction, Nitrogen sorption, Fourier-transform infrared spectroscopy, High-resolution transmission electron microscopy, Field emission scanning electron microscope, and X-ray photoelectron spectroscopy technique. Notably, the material possesses a high specific surface area with a proper microporous channel, which are the key parameters for achieving excellent electrocatalytic activity towards HER. The as-synthesized CoGLy catalyst displays the high catalytic efficiency with the overpotential of 125 mV to acquire the current density of 10 mA cm−2 and low Tafel slope of 72 mV dec−1. Also, the CoGLy catalyst shows outstanding stability in chronoamperometry measurement up to 25 h time without significant change in current density.

Novel synthesis of NaY-NH4F-Bi2S3 composite for enhancing iodine capture

Effective capture of radioactive iodine in spent fuel reprocessing is an urgent problem to be solved. In this study, we reported a novel fluoride modified bismuth sulfide supported NaY zeolite material (NaY-NH4F-Bi2S3), prepared by hydrothermal method. The zeolite with a hydrophobic skeleton was obtained by etching with NH4F solution. The adsorption mechanism generally follows preferential iodine enrichment in NaY zeolite microporous channels and is subsequently immobilized by loaded bismuth sulfide sites on NaY zeolite. Under the combination of physical and chemosorption, the sorption capacity of NaY-NH4F-Bi2S3 reaches 491 mg/g, which is much higher than that of bare NaY zeolite. The excellent thermal stability and radiation stability greatly enhance its iodine capture performance under harsh conditions. The comprehensive characteristics of high cost-effectiveness, low toxicity, good radiation resistance, and good thermal stability make it have potential applications in the capture, immobilization and storage of radioactive gaseous iodine during spent fuel reprocessing.

Effect of zeolite structure and addition of steam on naphtha catalytic cracking to improve olefin production

In this study, steam catalytic cracking of dodecane (a model representative of naphtha) was investigated both with and without steam. The reaction utilized the different 3D sinusoidal microporous channels in submicron ZSM-5 and BEA zeolite crystals to convert dodecane to light olefins. Although both synthesized submicron catalysts (400–500 nm) have similar Brønsted/Lewis acid ratios, the BEA zeolite exhibited higher surface acidity than ZSM-5 zeolite. In addition, the steam addition has significantly affected the zeolites structure, even though their cracking activity was not affected. However, the zeolites structural modification has shown significant effect on the pore shape selectivity which result in different light olefins yields. During catalytic cracking in the absence of steam, hydrogen transfer reaction was less favored over BEA zeolite, which result in higher light olefins selectivity and dry gas formation than with ZSM-5 zeolite. In the presence of steam, ZSM-5 pore-shape modification favored the monomolecular cracking pathway leading to achieving higher light olefin yield than that observed over BEA zeolite. The study demonstrated that ethylene/propylene ratio (E/P) is impacted by zeolite structure which is affected by the steam addition during the reaction.

A nanocaged cadmium-organic framework with high catalytic activity on the chemical fixation of CO2 and deacetalization-knoevenagel condensation

Heterogeneous MOFs catalysts have attracted great attention due to the efficient combination of heterogeneity (easy post-reaction separation and recyclability) and homogeneity (active sites and porosity), which inspire us to explore functional MOFs materials with higher catalytic activity on the chemical fixation of CO2 and deacetalization-Knoevenagel condensation. Herein, the self-assembly of Cd2+ and H6TDP under acidic solvothermal condition generated one cadmium-organic framework of {[(CH3)2NH2]2 [Cd2 (TDP) (H2O)2]⋅3DMF⋅2H2O}n (NUC-29, H6TDP = 2,4,6-tris(2,4-dicarboxyphenyl)pyridine) with nano-caged voids and hierarchical microporous channels, which were built on the combination of two kinds of mononuclear units of [Cd (1) (COO)3(H2O)] and [Cd (2) (COO)3(H2O)]. After the removal of solvent molecules by activation, NUC-29 possesses the coexistence of Lewis acid-base sites on the inner surface of channels including all exposed Cd2+ sites and Npyridine sites, which render it an excellent recyclable heterogeneous catalyst to facilitate the cycloaddition reaction of epoxides with CO2 and deacetalization-Knoevenagel condensation under mild conditions.

Enhancing adsorption capacities of low-concentration VOCs under humid conditions using NaY@meso-SiO2 core–shell composite

Y zeolite with high specific surface area and peculiar microporous channels has been regarded as a promising adsorbent in volatile organic compounds (VOCs) control. However, a scalable strategy for improving the hydrophobicity and mass diffusion of Y zeolite to remove VOCs remains a challenge. In this study, we successfully synthesized two NaY@meso-SiO2 core–shell composites with different shell thicknesses by coating NaY zeolite with mesoporous SiO2 (NaY@meso-SiO2-0.8 and NaY@meso-SiO2-1.2), which significantly improved the hydrophobicity of NaY zeolite and diffusion of VOCs into NaY zeolite. The results of XRD, SEM, TEM, FTIR and BET confirmed the successful synthesis of core–shell composites. The adsorption equilibrium experiments showed that coating NaY zeolite with mesoporous SiO2 effectively enhanced the hydrophobicity of NaY zeolite. Under RH = 0, the adsorption capacity of pristine NaY zeolite was the highest; while under RH = 50%, NaY@meso-SiO2-1.2 exhibited stronger adsorption ability and excellent hydrophobicity. The adsorption diffusion indicated that coating NaY zeolite with mesoporous SiO2 remarkably promoted the diffusion of VOCs into composites. Compared with the pristine NaY, core–shell composites showed higher diffusion coefficients and lower diffusion activation energy under RH = 0, particularly NaY@meso-SiO2-1.2. In addition, linear solvation energy relationships (LSERs) revealed that π-/n-electron pairs interaction became weak and dipolar interactions were enhanced when water was adsorbed on the surface of NaY@meso-SiO2-1.2. Hydrogen bonding decreased when RH level reached 50% and then increased with the increase of RH from 50% to 90%.

Numerical investigation on effects of induced magnetic field and viscous dissipation on MHD mixed convection in a vertical micro porous channel using Brinkmann – Forchheimer extended Darcy model

Impact of viscous dissipation and induced magnetic field in Brinkmann- Forchheimer extended Darcy flow of MHD mixed convectionsin a vertical microporous channel is investigated. Three different viscous dissipation models along with three different wall ambient temperature difference ratios are analysed. Projected results evidently indicate that the kind of viscous dissipation model has a notable impact on velocity distribution, induced magnetic field, current density, skin friction, and Nusselt number. It is found that an increase in Brinkman number increases velocity in the channel for distinct values of wall ambient temperatures difference ratios. Due to the domination of convection, an increase in Darcy number increases skin friction. The effect of induced current density on Darcy number, Brinkmann number, and inertial parameters are also discussed. The CFD data is used to train the built ANN model for predicting the heat transfer characteristics in the considered channel with 98.96% accuracy.

Novel microporous organic-inorganic hybrid metal phosphonates as electrocatalysts towards water oxidation reaction

In recent years, the development of electrochemical water oxidation requires an efficacious heterogeneous electrocatalyst to improve the high catalytic activity. Herein, newly designed three transition metal-based phosphonate materials i.e., cobalt phosphonate (CoEDA), nickel phosphonate (NiEDA), and nickel-cobalt phosphonate (NiCoEDA), were synthesized using etidronic acid (1-Hydroxyethane 1,1-diphosphonic acid) as the organophosphorus source under hydrothermal reaction condition at pH 6.5. Among these materials, CoEDA exhibits a high surface area with a proper microporous channel, one of the key parameters for showing excellent electrocatalytic activity towards oxygen evolution reaction (OER) with a lower overpotential (318 mV) and Tafel slope (70.1 mV dec−1). The superior catalytic activity towards OER can be correlated with the presence of the organic-inorganic hybrid material containing Co-O-P bond and the formation of highly electroactive cobalt oxyhydroxide (CoOOH) species onto the pore wall of the microporous channel. Besides, as-synthesized CoEDA catalyst displays outstanding catalytic stability for 25 h with a change in current density of only 6%.

Flexible MXene-based Janus porous fibrous membranes for sustainable solar-driven desalination and emulsions separation

Sustainable solar energy driven seawater desalination technology is currently deemed as a promising pathway to overcome the shortage of freshwater resources, but solar water evaporation material suffers from serious salt-fouling, low freshwater yield, and poor long-term performance in seawater. Herein, a Janus photothermal porous fibrous membrane, composed of hydrophobic MXene/Poly(dimethylsiloxane) coatings and a hydrophilic polylactic acid/TiO2 nanofluids porous fibrous membrane, was prepared. During the solar-driven seawater desalination process, the hydrophilic fibrous membrane, functioned as salt-rejection barrier, induced by TiO2 nanofluids and transport seawater to the surface through its microporous channels; the MXene/PDMS coatings acted as a photothermal layer and generated localized heat at the water-vapor interface upon light irradiation. The solar-thermal test results show that, the Janus porous fibrous membrane displays stable solar-thermal conversion efficiency of 60%, freshwater yield of 1 kg m-2 h-1 and low ion concentration (≤1 ppm) under 1 sun irradiation in direct contact mode, which is superior to other literatures reported. With synergistic effect of TiO2 nanofluids and MXene, the Janus fibrous membrane exhibits a high salt rejection rate of 99.95%, and antibacterial activity as high as of 100%. Notably, benefiting from opposite wettability of Janus porous fibrous membrane, the as-prepared membranes also display excellent separation flux and high separation accuracy (>99.95%) in various surfactant-stabilized oil/water emulsions. It is anticipated that this versatility of Janus porous fibrous membrane has excellent photothermal conversion capability and separation properties, making it have great application potential in using sustainable solar energy to collect freshwater from seawater, medical service wastewater and other application in environmental protection.

Heavy Metal Removal from Aqueous Solutions Using Fly-Ash Derived Zeolite NaP1

Fly-ash derived zeolites have recently -received great attention as cheaper adsorbents to remove heavy metals from water since they can be synthesized from a waste product. In this study, we evaluated the single- and multi-cation adsorption efficiencies of fly-ash derived NaP1 for the removal of zinc (Zn), copper (Cu) and lead (Pb). We also determined precipitation and leaching from NaP1 during the adsorption. Results showed that the uptake capacities for Zn (34 mg/g) and Pb (192 mg/g) were higher than other fly-ash derived NaP1 and adsorbents such as clinoptilolite and activated carbon. The Cu uptake was estimated ~ 14.6 mg/g. Pb2+ > Cu2+ > Zn2+ is the order for the metal cation selectivity of NaP1. Langmuir adsorption isotherm and pseudo-second order kinetic model fitted best for all elements. The metal uptake occurred in 15 min. Diffusion of hydrated metals through microporous channels is the rate-determining step.

Efficient and clean epoxidation of methyl oleate to epoxidized methyl oleate catalyzed by external surface of TS-1 supported molybdenum catalysts

Methyl oleate (MO) macromolecules are unable to access the microporous channel of conventional titanium silicalite-1 (TS-1) zeolite, which leads to the low catalytic activity of epoxidation of MO. Herein, the small-size TS-1 (TS-1-s) zeolite with a large surface area was synthesized successfully through steam-assisted crystallization, and then a novel blocked TS-1-s supported molybdenum (Mo/TS-1-bs) catalysts were prepared for efficient epoxidation of MO with clean H 2 O 2 to produce epoxidized methyl oleate (EMO). Various characterization results show the introduced Mo species are highly dispersed on the outer surface of TS-1-s without destroying the structure of the MFI type zeolite and the tetrahedral framework titanium (Ti 4+ ). Interestingly, a large number of Mo 6+ species exhibit certain epoxidation activity attributing to the generating of electrophilic molybdenum hydroperoxide (Mo–OOH) species via Mo species combined with H 2 O 2 , which could adsorb and react easily with MO molecules. Furthermore, the Mo species are also coordinated with Ti 4+ species through the O atom resulting in the facile attack of the Ti–O bonds by H 2 O 2 and easy to form an active intermediate. Therefore, compared with the conventional TS-1, the Mo/TS-1-bs shows higher catalytic activity in the epoxidation reaction. However, the acidity of Mo/TS-1-bs catalysts increases with increasing the Mo-loading owing to the formation of Lewis acid, which leads to the side reactions and the decrease of EMO selectivity. As a consequence, the efficient, non-corrosive and green catalytic system for epoxidation of MO was developed, and the activity improvement of Mo species and the influence of acid were also demonstrated. • The clean small-size TS-1 and Mo/TS-1-bs catalysts were prepared successfully for epoxidation of methyl oleate (MO). • Mo species can promote the MO epoxidation through generating of molybdenum hydroperoxide and coordination with Ti 4+ . • The acidity of Mo/TS-1-bs catalysts can decrease the selectivity of epoxidized methyl oleate.

Piperazine-Linked Covalent Organic Frameworks with High Electrical Conductivity.

A new kind of piperazine-linked covalent organic framework (COF) was synthesized through the nucleophilic substitution reaction between octaminophthalocyanines and hexadecafluorophthalocyanines. The two-dimensional (2D) frameworks are in tetragonally shaped polygon sheets, which stack in an AA stacking mode to constitute periodically ordered metallophthalocyanine columns and one-dimensional (1D) microporous channels. The piperazine-linked COFs exhibit excellent chemical stability and permanent porosity. By virtue of the neatly arrayed phthalocyanine columns and inbuilt cationic radicals, the piperazine-linked frameworks are highly conductive. The conductivity values of NiPc-NH-CoPcF8 COF reached up to 2.72 and 12.7 S m-1 for pellet and film samples, respectively. Moreover, this p-type conductive COF exhibited a high carrier mobility of 35.4 cm2 V-1 s-1. Both the electric conductivity and carrier mobility set new records for conductive COFs.

Tuning the location of Pd on HY zeolite by a dual-solvent method for efficient deep hydrogenation saturation of naphthalene

Tuning the location of metal on the support is of great importance for catalyst performance optimization, which is hardly realized by the traditional impregnation method. Herein, a dual-solvent method using dichloromethane and water has been developed for the preparation of Pd/HY catalysts via evaporation-induced aggregation of Pd(OAc)2. The state and location of Pd nanoparticles on HY can be effectively tuned by the water content in the dual-solvent system. Due to the filling of partial micropore channels by certain amount of water, hydrophobic Pd(OAc)2 is selectively deposited on the un-occupied surface of HY, which is verified by the changes in textural and acid properties of the Pd/HY catalysts. FT-IR spectra illustrate the reconstruction of tridimensional Pd3(CH3COO)6 trimer in solution to the planar bidentate Pd(II) acetate species on HY surface, which guarantees the stable loading of active Pd nanoparticles on HY. Pd nanoparticles selectively loaded around the junctions of micropores and mesopores of HY zeolite by moderate amount of water have been demonstrated to be highly active for the deep hydrogenation saturation of naphthalene. Due to the selective locating of Pd nanoparticles in the properly open space of HY, the B acid sites are well maintained and efficiently utilized for the enhanced anchoring of Pd nanoparticles and facilitated diffusion of the reactants. Therefore, the optimum Pd/HY catalyst possesses highly dispersed and electron-deficient Pd nanoparticles, and exhibited superior performance of hydrogenation saturation. The dual-solvent strategy can be applied to other zeolite systems to selectively loading of Pd nanoparticles for various catalytic applications.

Investigation of Surface Properties of Eggshell based Kappa-Carrageenan-Polyvinyl Alcohol Nanobiocomposite Coated Low Alloyed Steel Foam

In this study, we developed a novel eggshell based kappa-carrageenan-polyvinyl alcohol nanobiocomposite coated low alloyed steel foam. The prepared nanobiocomposite was preferred as a coating function on the distribution of particles on the low alloyed steel foam. The scanning electron microscopy (SEM), stereo microscope, and fourier transform infrared spectroscopy (FT-IR) techniques were used to determine the chemical and surface properties of the nanobiocomposite and nanobiocomposite coated low alloyed steel foam. According to the characterization results, we observed that the nanobiocomposite coated low alloyed steel foam had a uniform controlled morphology. Furthermore, the mean surface roughness values of uncoated low alloyed steel foam and nanobiocomposite coated low alloyed steel foam were measured as 4.48 µm and 4.61 µm, respectively. Consequently, we showed that the nanobiocomposite was uniformly coated onto the surface of the micropore channel of the low alloyed steel foam. Based on these results, eggshell based kappa-carrageenan-polyvinyl alcohol nanobiocomposite is a promising nanomaterial for surface modification of the low alloyed steel foam with a controlled and homogeneously distributed surface feature in biomedical applications using a green approach.

Preparation and infiltration of NASICON-type solid electrolytes with microporous channels

A lithium-ion conductor with microporous channels (p-LATP) was prepared by using templates from a hydrothermal-assisted sol-gel method, and the as-prepared p-LATP was infiltrated to obtain p-LATP and d-LATPs composites in this work. SEM photos showed that the morphologies of p-LATP, d-LATP, and p-LATP and d-LATP composites were quite similar. XRD analysis showed that the crystallographic structures were also similar. TEM examinations revealed that microporous channels existed in the pure p-LATP and the p-LATP and d-LATP composites but not in the pure d-LATP. The total conductivities of the composites were higher than those of the pure p-LATP and pure d-LATP. The enhancement of the total conductivity of the composites was ascribed to the interaction of microporous channels and dense lithium-ion conducting areas. The promising results obtained in this work provide a new way to prepare solid lithium-ion conductors.