Microporous Channels Research Articles

Generating Beta Zeolite Nanosheets of Intergrown Polymorph B and C Using Polycationic Structure-Directing Agent.

Zeolitic nanosheets possess great potential in catalysis due to their enhanced transport property and accessibility toward bulky molecules compared to conventional micron- meter scale crystals. However, the generation of Beta zeolite nanosheets, which are crucial for industrial catalysis, is still challenging for its intergrowth nature. In this work, aluminosilicate Beta nanosheets of ca. 16nm thick with house-of-cards architecture are generated using a special polycationic organic structure directing agent (OSDA), [-N+(CH3)2-C5H10-N+(CH3)2-C6H12-]n[Br-]2n, in greener hydroxide media. Transmission electron microscopy and electron tomography reconstruction revealed that the nanosheets are composed of unprecedented intergrowth of polymorphs B and polymorph C (i.e., BEC topology), possessing only straight micropore channels. 2D 29Si{1H} and 27Al{1H} heteronuclear correlation NMR spectra reveal that the framework Al atoms are mainly situated close to the ammonium moieties of the OSDA inside straight channels, owing to a strong OSDA-framework attraction. The selectivities of ethylene, propylene and catalyst lifetime have been promoted in n-heptane cracking, due to stronger acidity and enhanced diffusion property. Moreover, the architecture is robust toward deep dealumination and Ti- modification, allowing it to be a superior catalyst in cyclohexene epoxidation. The polycation OSDA design concept and the recipe for Beta nanosheets may find broader applications in catalysis.

Functionalization of zeolite-encapsulated Cu5 clusters as visible-light photoactive sub-nanomaterials.

The unique structural properties of zeolites make them ideal environments for encapsulating subnanometric metal clusters on their microporous channels and cavities, showing an enhanced catalytic performance. As a first step towards the functionalization of these clusters as photocatalysts as well, this work addresses the optical properties of zeolite-encapsulated Cu5-TiO2 nanoparticles as well as their application in the photo-induced activation of CO2 by sunlight. Model density functional theory (DFT) calculations indicate the stability of the Cu5 cluster adsorbed on the TiO2 nanoparticles filling the pores of a model zeolite structure. Second, it is shown that while TiO2 nanoparticles absorb in the UV, the photo-absorption spectrum of the Cu5-TiO2 nanoparticle composite is peaked at the visible region, where the sun has its maximum energy input, also allowing for the photo-induced activation of CO2 adsorbed onto the Cu5 cluster.

Generating Disk-Shaped MTW Zeolite with Reduced Channel Length Using Polycation Structure-Directing Agent for Hydroisomerization of N-Dodecane

The development of hierarchically structured zeolites to mitigate diffusion limitations and improve catalytic performance constitutes a focus of current research. In this study, we present the synthesis of hierarchical disk-shaped MTW zeolite (ZSM-12-P) with shortened channel length using polycation [-C5H9N+C10H10N+C5H9-C3H6-]n[Br−]2n (PDIP) as an organic structure-directing agent (OSDA). The ZSM-12-P zeolite forms disk-shaped structures with thicknesses ranging from 140 to 160 nm and exhibits rotational intergrowth. These structures are composed of interconnected nanocrystalline domains that form mesopores accessible from the outer surface, while the microporous channels extend along the thickness direction. In addition, the polycationic OSDA possesses strong interaction with framework and MTW structure-directing ability, enabling the successful synthesis of the Al-rich ZSM-12-P. Owing to its strong acidity and improved diffusion property, the Pt/HZSM-12-P catalyst demonstrates enhanced catalytic n-dodecane hydroisomerization activity and isomer yield.

Evaluation of innovative drying technologies in Gardenia jasminoides Ellis drying considering product quality and drying efficiency

Gardenia jasminoides Ellis is widely used as healthy food and herbal medicine for its anti-inflammatory, analgesic, antihypertensive, and antiviral functions. The drying behavior and physicochemical quality of Gardenia jasminoides Ellis were studied to evaluate its adaptability under four drying techniques: hot air drying (HAD), medium-and short-wave infrared drying (MSWID), pulsed vacuum drying (PVD), and radio frequency-HAD (RF-HAD). Compared with HAD and MSWID, PVD and RF-HAD can form beneficial microporous channels for moisture migration inside Gardenia jasminoides Ellis, thus shortening drying time by 32.56–42.51 % and increasing geniposide content by 3.31–13.77 %, while better preserving the brightness and redness. In addition, Pearson correlation analysis confirmed the RF-HAD dried samples showed the best antioxidant activity with the highest content of active ingredients (chlorogenic acid, geniposide), and there was a significant positive correlation between sample color and yellow pigment content. After comprehensive comparison, RF-HAD is proposed to be the most suitable method for Gardenia jasminoides Ellis drying. This research could provide scientific basis and technical support for promoting the high quality development of industrial processing of Gardenia jasminoides Ellis.

Constructing new-generation ion exchange membranes under confinement regime.

Ion exchange membranes (IEMs) enable fast and selective ion transport and the partition of electrode reactions, playing an important role in the fields of precise ion separation, renewable energy storage and conversion, and clean energy production. Traditional IEMs form ion channels at the nanometer-scale via the assembly of flexible polymeric chains, which are trapped in the permeability/conductivity and selectivity trade-off dilemma due to a high swelling propensity. New-generation IEMs have shown great potential to break this intrinsic limitation by using microporous framework channels for ion transport under a confinement regime. In this Review, we first describe the fundamental principles of ion transport in charged channels from nanometer to sub-nanometer scale. Then, we focus on the construction of new-generation IEMs and highlight the microporous confinement effects from sub-2-nm to sub-1-nm and further to ultra-micropores. The enhanced ion transport properties brought by the intense size sieving and channel interaction are elucidated, and the corresponding applications including lithium separation, flow battery, water electrolysis, and ammonia synthesis are introduced. Finally, we prospect the future development of new-generation IEMs with respect to the intricate microstructure observation, in-situ ion transport visualization, and large-scale membrane fabrication.

Semiflexible spiro-branched membrane with adjustable sub-nanoscale channels and high positive charge for acid recovery

Acid recovery from industrial wastewater based on membrane separation is an essential technology to improve the economic efficiency and environmental friendliness. However, the low recovery efficiency and trade-off between acid permeability and selectivity of membrane materials have hindered the widespread application of this technology. In this study, we developed a spiro-branched membrane with semiflexible three-dimensional (3D) network structure by utilizing rigid contorted units as branching nodes. The semiflexible 3D network structure led to inefficient chain packing and the creation of numerous sub-nanoscale microporous ion channels, with sizes that can be finely adjusted. Furthermore, this 3D network structure allows the membrane to maintain low swelling and excellent stability while being enriched with positively charged groups. Ultimately, the optimally tuned membrane separator demonstrated an outstanding H+ dialysis coefficient (up to 108.6 × 10−3 m h−1), good selectivity (42.2) and high stability, surpassing both commercial membranes and those reported recently.

Boosting hydroisomerization of n-hexadecane by designing core-shell bifunctional catalysts with partially blocked micropores

Hydroisomerization of long-chain n-alkanes is an indispensable route for upgrading fossil fuels and lubricant oils to meet the state of art regulations. Precisely regulate the distribution of acidic and metal active sites to suppress unwanted cracking reaction is hitherto a difficult task. In this work, we develop a simple coating-carbonation strategy for constructing novel core-shell bifunctional catalysts, comprising ZSM-22 zeolite core with the partially blocked channels and Pt nanoparticles loaded on the mesoporous SiO2 shell. The unique treatment not only adjusted the distribution of acid sites located within the micropore channels and external surface, but also alter the locations and dispersion of Pt nanoparticles. Owing to the short diffusion lengths, nanoscale distance between acid sites and Pt species, and high metal dispersions, the core-shell bifunctional catalyst exhibits outperformed performance in n-hexadecane hydroisomerization, i.e., the yield of isomerized hexadecane can reach 87.9 %, which is among the relatively high level compared with the previous reported Pt/zeolite counterparts. Moreover, the catalyst also displays excellent stability (no deactivation within 100 h). The disclosed structure-catalysis relationship provides rational reference for designing the synergistic meta-acid active sites in the hydroisomerization of long-chain n-alkanes.

A core–shell hierarchically porous ZSM-5 zeolite with an Al-rich shell synthesized by using hydrolysable templates

Hierarchically porous zeolites with both macroporous/mesoporous and microporous channels have received significant attention due to their better catalytic performance than that of conventional zeolites. Here, for the first time, a template with hydrolysable groups that can achieve in-situ regulation of the pH value has been designed. Employing this novel template, core–shell hierarchically porous ZSM-5 zeolites with Al-rich shells were one-step synthesized, which exhibit better catalytic activity and selectivity than conventional microporous zeolites in bulky-molecule catalysis.

Effect of ultrasound power on moisture status change of apple by contact ultrasound reinforced far-infrared radiation drying

To explore the effect of ultrasound power on internal water change of apple dried by contact ultrasound enhanced far-infrared radiation drying (CUFRD), the drying characteristics, microstructure, moisture migration, and molecular vibration patterns of apple slices subjected to this process at different ultrasound powers were investigated using low-field nuclear magnetic resonance (LF-NMR), Near-infrared (NIR) and two-dimensional(2D) correlation analysis. With the increase of contact ultrasound (CU) power, the drying times of apple were shortened by 8.69% to 17.39%, respectively. Scanning electron microscopy (SEM) observation indicated that higher CU power resulted in an increase in the number of microporous channels and pore diameter within apple’s internal tissue. The findings of LF-NMR clarified that free water content kept decreasing, while the content of semi-bound water initially increased and then reduced. Magnetic resonance imaging (MRI) images illustrated that higher CU power corresponded to a faster decrease in the redness value of the H+ density map of apple during drying. 2D correlation analysis revealed that the changes in the O-H bonds of apple were prioritized over the C-H bonds during drying process. NIR spectroscopy and LF-NMR heterogeneous correlation spectrograms demonstrated that at wavelengths of 950, 1450, and 1680 nm, the order of changes in water-related functional groups was quadruple-frequency O-H > combination of the first overtone of O-H stretching and OH-bending band > double-frequency C-H. Moreover, with increasing CU power, the vibration of hydrogen-containing functional groups intensified, leading to increased water activity. Thus, CU application could significantly enhance the CUFRD process of apple slices.

Rice husk-based activated carbon/carbon nanotubes composites for synergistically enhancing the performance of lead-carbon batteries

Lead-carbon batteries (LCBs), an advanced form of lead-acid battery (LAB) technology, incorporate super-capacitive carbon materials into the negative electrode. Rice husk-based activated carbon (RHAC) is a promising additive for LCBs due to its favorable properties. However, RHAC's amorphous structure impedes electronic conduction, and its zigzag microporous channels hinder ion transport, leading to degraded high-rate performance. This study addresses these issues by growing carbon nanotubes (CNTs) in situ on RHAC through a one-step heat treatment, resulting in carbon nanotubes-loaded RHAC (CNTs/RHAC), and the electronic conductivity and ionic conductivity are simultaneously enhanced. When CNTs constitute 30 wt% of CNTs/RHAC, the negative electrode achieves a cycle life of 4721 cycles at a 2C rate under 50 % state of charge, which is 10.04 times that of the blank anode. The enhanced performance is attributed to the synergistic effects of CNTs and RHAC, where CNTs form long-range conductive networks among the negative electrode active material (NAM) and facilitate the diffusion and electro-deposition of Pb2+, while the high specific surface area (SSA) and hierarchical porous structure of RHAC enhance its capacitive function, leading to a stable lead-carbon composite structure.

Mesoporogen-free synthesis of hierarchical SAPO-11 from kaolin for hydroisomerization of n-alkanes

Hierarchical SAPO-11, featuring both micropore and mesopore channels, demonstrates an outstanding performance in high-octane gasoline production. In this work, we propose an economic and effective approach to directly fabricate hierarchical SAPO-11 molecular sieve from natural kaolin, eliminating the need for mesoporogens. The systematic characterization results show that the kaolin-derived SAPO-11 possesses abundant micro-mesoporous structure and more Brønsted (B) acid sites on the external surface in contrast with the conventional SAPO-11 prepared employing silica sol as silicon source as well as SAPO-11 synthesized with the assist with of poly(ethylene oxide)-block-poly(propylene oxide)-block-poly(ethylene oxide) (F127). The analysis of the formation process reveals that the kaolin not only provides silicon source for the SAPO-11 crystal growth, but also offers confined environment for crystal growth along the preferential orientation, resulting in the generation of the microporous and mesoporous structure. Benefiting from these unique properties, the kaolin-derived Pt/SAPO-11 exhibits considerably improved selectivity for di-branched C8 isomers in n-octane hydroisomerization.

Three-dimensional linker-promoted hierarchical porous metal–organic framework for natural gas purification

The purification of methane from natural gas is extremely important for industrial applications. In this study, hierarchical porous material LIFM-Z1 with microporous cages and mesoporous hexagonal one-dimensional channels was successfully synthesized and evaluated. The results show that LIFM-Z1 can effectively separate CH4 from the mixed gas containing CH4, C2H6, C3H8 and n-C4H10. Single-component adsorption experiments revealed the selective adsorption ability of LIFM-Z1 for C2H6, C3H8, and n-C4H10, enabling a clear distinction between these components and CH4. This selectivity was further verified by dynamic breakthrough experiments. Theoretical analysis shows that the interaction between LIFM-Z1 and gas molecules mainly depends on the synergistic effect of C–H⋯O hydrogen bond and C–H⋯C van der Waals force. The results highlight the potential of utilizing 3D linkers to enhance the inner wall interaction with CH4 and its related gases in MOF construction. These characteristics of LIFM-Z1 not only successfully demonstrate the potential of separation and purification of natural gas with high efficiency, but also show its broad application prospects in the actual natural gas processing.

A high-performance watermelon skin ion-solvating membrane for electrochemical CO2 reduction

Ion-solvating membranes have been gaining increasing attention as core components of electrochemical energy conversion and storage devices. However, the development of ion-solvating membranes with low ion resistance and high ion selectivity still poses challenges. In order to propose an effective strategy for high-performance ion-solvating membranes, this study conducted a comprehensive investigation on watermelon skin membranes through a combination of experimental research and molecular dynamics simulation. The micropores and continuous hydrogen-bonding networks constructed by the synergistic effect of cellulose fiber and pectin enable the hypodermis of watermelon skin membranes to have a high ion conductivity of 282.3 mS cm−1 (room temperature, saturated with 1 M KOH). The negatively charged groups and hydroxyl groups on the microporous channels increase the formate penetration resistance of watermelon skin membranes in contrast to commercially available membranes, and this is crucial for CO2 electroreduction. Therefore, the confinement of proton donors and negatively charged groups within three-dimensional microporous polymers gives inspiration for the design of high-performance ion-solvating membranes.

Development of ternary hybrid nanofluid for a viscous Casson fluid flow through an inclined micro-porous channel with Rosseland nonlinear thermal radiation

ABSTRACT The current problem is concerned with the investigation of Casson ternary hybrid nanofluid flow through microchannel. Nanofluids containing three distinct kinds of nanoparticles have a lot of industrial and engineering applications as a result of their amazing thermal properties. The nanoparticles (alumina A l 2 O 3 , titanium oxide Ti O 2 , and copper oxide CuO ) are immersed in base fluid (ethylene glycol C 2 H 6 O 2 ) resulting in ternary hybrid nanofluid ( A l 2 O 3 + Ti O 2 + CuO / C 2 H 6 O 2 ). For the problem under consideration, the momentum distribution, temperature distribution, entropy generation, and Bejan number have been examined. With the aid of tables and graphs, comparisons of ternary hybrid, binary hybrid, and mono nanofluids have also been investigated. With nondimensional variables, the governing equations are transformed into a dimensionless form and solved using the Chebyshev Collocation Method (CCM). Analysis shows that the increment in Reynolds number, Brinkmann number, and exponential heat source parameter results in an enhancement in the dimensionless temperature and the variational improvement of the thermal radiation parameter reduces the thermal distribution. Hence, the findings show that ternary hybrid nanofluids perform better in terms of thermal conductivity performance than either binary hybrid or mono nanofluids.

Preparation of slow-release carbon source fillers from agricultural solid waste for efficient nitrogen removal from municipal wastewater: Removal performance, microbial community and mechanisms

In this study, five types of agricultural wastes, were used as alternative materials for slow-release carbon source, alternative materials were prepared as slow-release carbon source fillers (ZCF) using a no-sintering method, and studied by leaching elements, carbon release, nitrification and denitrification potential, and bio-attachment performance, walnut shell-based filler was found to have better performance in terms of persistence of carbon release, impact stability, carbon biochemistry and green safety. When HRT was 8 h in H-O, 12 h in H-A, and R was 100 % and C/N was 2 in H-Z BAF, the average concentrations of effluent NH4+-N and TN were only 0.4 and 12.2 mg/L, which achieved the high efficiency and economy of H-Z BAF under low C/N conditions. The newly prepared ZCF had a rougher outer surface, a uniformly distributed flocculent structure and numerous microporous channels on the inner surface, and the carbon source inside the filler was degraded or transformed by microorganisms, as compared to the filler in H-O and H-A at the later stage of use. The abundance of nitrifying bacteria, denitrifying bacteria was increased in the H-Z BAF, and that functional CAZymes were enriched and involved in the degradation of cellulose and hemicellulose, can be efficiently utilized by microorganisms. This study provides technical support for the development of cheap, stable and efficient slow-release carbon sources and their application in denitrification of municipal wastewater plant tailwater.

A Microporous Channel Copper Immersion Layer Promotes the Rapid Ni-P Electroless Plating Process on Aluminum Alloys at Medium and Low Temperatures

Electroless plating is a commonly used method to enhance the corrosion resistance, wear resistance, and decorative performance of aluminum alloys. However, in electroless plating processes, it is customary to maintain the solution temperature at levels exceeding 85 °C, a critical condition that ensures a sufficiently rapid deposition rate and thereby fosters the formation of high-performance coatings. Conventional immersion pretreatments with zinc and palladium result in lower deposition rates at low temperatures. This study shows that a copper immersion layer with microporous channels can facilitate the electroless plating process for aluminum alloys at lower temperatures. Through a redox reaction in a Cu2+-containing solution at 70 °C, a copper immersion layer with a microporous structure could be created on an aluminum alloy. The microporous channels between the copper immersion layer and the aluminum alloy create electrochemical corrosion cells in the plating solution, accelerating the electroless plating process. The Ni-P coating obtained after pretreatment by copper immersion has a higher hardness (578 HV) and a lower corrosion current density (0.55 μA cm−2). This work provides a practical method to rapidly fabricate high-performance Ni-P coatings at intermediate temperatures (70 °C–75 °C).

Nanofiber membranes fabricated by coaxial electrospinning with porous channel structure for high-efficiency oil-water separation

The electrospinning nanofiber membranes modified by nanoparticles can effectively improve anti-oil adhesion and separation performance. However, the low stability of nanoparticles on the fiber membrane surface substantially limits the operational lifespan of the membrane. Herein, poly(vinylidene fluoride) (PVDF) nanofiber membranes with multi-scale microporous channel structures are prepared using coaxial electrospinning and a sacrificial template strategy. Subsequently, iron phytate nanoparticles are grown in situ on the fibers to fill the porous structures by utilizing the hollow and porous nanofibers as a framework. The interlocking structure between the nanoparticles and the porous fibers significantly enhances the stability and durability between nanoparticles and the fiber membrane. Even after being subjected to ultrasonic treatment for 7 h, there is no discernible shedding of nanoparticles from the fiber membrane. The prepared nanofiber membrane demonstrates exceptional superhydrophilicity and underwater superoleophobicity, exhibiting remarkable self-cleaning capability and resistance to crude oil contamination. Additionally, the membrane efficiently separates various oil-in-water emulsions, achieving a high separation efficiency of over 99%. Moreover, the membrane also demonstrates excellent adsorption capability towards cationic dyes. Therefore, this interlocking structure composed of nanoparticles and nanofibers presents new ideas and insights for the preparation of high-performance and durable oil–water separation membranes.

Hierarchical Y Zeolite-Based Catalysts for VGO Cracking: Impact of Carbonaceous Species on Catalyst Acidity and Specific Surface Area.

The performance of catalysts prepared from hierarchical Y zeolites has been studied during the conversion of vacuum gas oil (VGO) into higher-value products. Two different catalysts have been studied: CatY.0.00 was obtained from the standard zeolite (Y-0.00-M: without alkaline treatment) and CatY.0.20 was prepared from the desilicated zeolite (Y-0-20-M: treated with 0.20 M NaOH). The cracking tests were carried out in a microactivity test (MAT) unit with a fixed-bed reactor at 550 °C in the 20-50 s reaction time range, with a catalyst mass of 3 g and a mass flow rate of VGO of 2.0 g/min. The products obtained were grouped according to their boiling point range in dry gas (DG), liquefied petroleum gas (LPG), naphtha, and coke. The results showed a greater conversion and selectivity to gasoline with the CatY.0.20 catalyst, along with improved quality (RON) of the C5-C12 cut. Conversely, the CatY.0.00 catalyst (obtained from the Y-0.00-M zeolite) showed greater selectivity to gases (DG and LPG), attributable to the electronic confinement effect within the microporous channels of the zeolite. The nature of coke has been studied using different analysis techniques and the impact on the catalysts by comparing the properties of the fresh and deactivated catalysts. The coke deposited on the catalyst surfaces was responsible for the loss of activity; however, the CatY.0.20 catalyst showed greater resistance to deactivation by coke, despite showing the highest selectivity. Given that the reaction occurs in the acid sites of the zeolite and not in the matrix, the increased degree of mesoporosity of the zeolite in the CatY.0.20 catalyst facilitated the outward diffusion of products from the zeolitic channels to the matrix, thereby preserving greater activity.

In-situ glass transition of ZIF-62 based mixed matrix membranes for enhancing H2 fast separation

Mixed matrix membranes (MMMs), combining the advantages of polymer membranes and porous materials, processing the potential to realize large-scale gas separation applications. However, the interfacial defects in MMMs greatly hindered gas separation performance improvement. Therefore, designing an MMM with high loading and good interfacial compatibility remains a critical issue in promoting the application of MMMs. Herein, during in-situ heating process, the melting of liquid ZIF-62 in PBI polymer can largely fill the interfacial defects in MMMs. The microporous transport channels of ZIF-62 glass in MMMs promoted the H2 diffusion and inhibited the CO2 and CH4 diffusion, thus enhancing the H2/CO2 and H2/CH4 separation of MMMs. For mixed gas testing, the 45 wt% ZIF-62 glass/PBI membrane had the maximum H2 permeability of 459 barrer, and its H2/CO2 and H2/CH4 selectivities were 23 and 57, higher than the gas separation upper bonds. In addition, ZIF-62 glass/PBI membrane exhibited stable separation performance under 1–5 bar pressure. Therefore, the rational combination of MOF glass and polymer matrix could provide promising potential for reducing the interfacial defects of high-loading MMMs, thus enhancing the gas separation performance.

A Synergetic Pore Compartmentalization and Hydrophobization Strategy for Synchronously Boosting the Stability and Activity of Enzyme.

Spatial immobilization of fragile enzymes using a nanocarrier is an efficient means to design heterogeneous biocatalysts, presenting superior stability and recyclability to pristine enzymes. An immobilized enzyme, however, usually compromises its catalytic activity because of inevasible mass transfer issues and the unfavorable conformation changes in a confined environment. Here, we describe a synergetic metal-organic framework pore-engineering strategy to trap lipase (an important hydrolase), which confers lipase-boosted stability and activity simultaneously. The hierarchically porous NU-1003, featuring interconnected mesopore and micropore channels, is precisely modified by chain-adjustable fatty acids on its mesopore channel, into which lipase is trapped. The interconnected pore structure ensures efficient communication between trapped lipase and exterior media, while the fatty acid-mediated hydrophobic pore can activate the opening conformation of lipase by interfacial interaction. Such dual pore compartmentalization and hydrophobization activation effects render the catalytic center of trapped lipase highly accessible, resulting in 1.57-fold and 2.46-fold activities as native lipase on ester hydrolysis and enantioselective catalysis. In addition, the feasibility of these heterogeneous biocatalysts for kinetic resolution of enantiomer is also validated, showing much higher efficiency than native lipase.