Changes In Pore Size Research Articles

Evolution of Pore Reorganization of Porous Silicon

To obtain a closed and smooth surface of a porous Si layer for an epitaxial growth of a silicon wafer, the porous Si must be reorganized. To understand the reorganization process, the evolution of the pores is investigated in this contribution. The reorganization process is interrupted at different stages and cross-sectional SEM images are taken to evaluate the change in pore size and shape during reorganization. Additionally, the stress is measured using XRD. At the beginning of the reorganization of the pores, the as-etched columnar pores with diameters of about 5 nm become coarser with larger diameters. At temperatures above 900°C, the surface closes and thus becomes smooth. In addition, the form of the pores starts to change from columnar to round with diameters between 55-65 nm. When the highest temperature of 1100°C is reached, the columnar pores have disappeared and the pores are round and faceted. With an additional plateau time of up to 20 min, there is no visible change in pore faceting. The as-etched sample shows tensile stress and the sample annealed at 700°C is nearly unstressed. When the temperature is increased beyond 900°C, the stress is compressive and no further change is visible.

The theoretical freezing model of sandstone considering the statistical arrangement of pore structure

It is of great significance to understand the evolution law of unfrozen water content in frozen rocks to maintain the stability of geotechnical engineering in cold regions. Due to the different particle sizes and shapes, coupled with the diversity of cements, the internal pore structures of rocks are complex and diverse. In this study, a theoretical model for freezing point of sandstone is proposed based on the characteristics of microscopic pore structures. The characteristic of freezing point is analyzed by considering the mineral particle arrangement. A statistical theoretical model of unfrozen water in sandstone is established according to the random arrangement of mineral particles. The influence of the stacking angle of mineral particles following the normal distribution on unfrozen water content is analyzed. Finally, the NMR freezing process analysis for sandstones was carried out. The results show that the statistical theoretical model of unfrozen water fits the experimental results well. The effect of the average value of stacking angle on unfrozen water content is mainly due to the change of pore size, which leads to the change of pore water content. The standard deviation of stacking angle determines the residual water content.

Flexible Mesopores in Nanoscrolls: Extraordinarily Large Alteration of Pore Sizes and Their Reversibility.

Flexible porous materials have gained considerable interest for their potential applications in selective absorption and controlled release/storage of specific molecules or compounds. Here, nanoscrolls are proposed as a type of inorganic solids with reversibly flexible mesopores. Nanoscrolls exhibit a rolled-up structure composed of nanosheets with a 1D rod-like morphology, possessing two distinct nanospaces. The first space comprises 1D tubular mesopores located at the center of the rod, while the second space exists in the interlayer regions on the wall of the mesopore, resulting from the layer stacking caused by the scrolling of nanosheets. By replacing the interlayer cations on the nanoscroll walls with other cations, a drastic alteration in the size of the 1D mesopores is observed. For instance, exchanging bulky dodecylammonium cations with small NH4 + cations leads to a substantial change in pore size, with differences ranging from 10 to 20nm-a notably larger variation compared to previous reports on flexible porous materials. Importantly, the alteration of pore size induced by the exchange reaction is found to be reversible. This reversible alteration in pore size holds promise for applications in host-guest chemistry involving large moieties such as nanoparticles and enzymes.

Chlorella-enriched hydrogels protect against myocardial damage and reactive oxygen species production in an in vitro ischemia/reperfusion model using cardiac spheroids

Microalgae have emerged as promising photosynthetic microorganisms for biofabricating advanced tissue constructs, with improved oxygenation and reduced reactive oxygen species (ROS) production. However, their use in the engineering of human tissues has been limited due to their intrinsic growth requirements, which are not compatible with human cells. In this study, we first formulated alginate-gelatin (AlgGel) hydrogels with increasing densities ofChlorella vulgaris. Then, we characterised their mechanical properties and pore size. Finally, we evaluated their effects on cardiac spheroid (CS) pathophysiological response under control and ischemia/reperfusion (I/R) conditions. Our results showed that the addition ofChlorelladid not affect AlgGel mechanical properties, while the mean pore size significantly decreased by 35% in the presence of the 107cells ml-1microalgae density. Under normoxic conditions, the addition of 107Chlorellacells ml-1significantly reduced CS viability starting from 14 d in. No changes in pore size nor CS viability were measured for hydrogels containing 105and 106Chlorellacells ml-1. In our I/R model, allChlorella-enriched hydrogels reduced cardiac cell sensitivity to hypoxic conditions with a corresponding reduction in ROS production, as well as protected against I/R-induced reduction in cell viability. Altogether, our results support a promising use ofChlorella-enriched Alg-Gel hydrogels for cardiovascular tissue engineering.

Unveiling the pore size change in polyamide membrane using aggregation induced emission

Polyamide (PA) membranes play a crucial role in nanofiltration and reverse osmosis separations, while their pore size is primary to determine the separation performance. Current methods for pore size analysis, such as atomic force microscopy (AFM), positron annihilation spectroscopy (PAS), and the filtration experiment of neutral molecules are time-consuming and lack real-time capabilities. This limitation hinders in-situ monitoring of pore size dynamics under various operating conditions. Therefore, a rapid and real-time method is highly desirable for pore size analysis. This work presents a novel approach for real-time detection of pore size variations in PA membranes under different solvent conditions. It utilizes aggregation-induced emission (AIE) with tetraphenylethylene (TPE) groups covalently linked to the PA polymer chain during interfacial polymerization using 1-(4-Aminophenyl)-1,2,2-triphenylethene as a co-monomer. Fluorescence intensity of the PA membrane serves as an indicator of the confined state of the TPE molecules within the polymer network, thereby reflecting pore size changes under various conditions. The accuracy of the AIE-based approach is validated through complementary analyses such as small-angle X-ray scattering (SAXS) and rejection of dye molecules. The observed consistency between fluorescence variations in the PA membrane and pore size changes under different solvent conditions confirms the effectiveness of this method. This work provides a valuable visual tool for in-situ monitoring of pore size dynamics in polyamide membranes.

Hyperelastic constitutive relations for porous materials with initial stress

Initial stress is widely observed in porous materials. However, its constitutive theory remains unknown due to the lack of a framework for modeling the interactions between initial stress and porosity. In this study, we construct the porous hyperelastic constitutive model with arbitrary initial stresses through the multiplicative decomposition approach. Based on the compression experiment of shale samples, the parameters in the constitutive equation are determined. Then, the explicit equations of in-plane elastic coefficients are proposed by linearizing the finite deformation formulation. The influences brought by the coexistence of initial stresses and porosity on these coefficients are revealed. Later, comparative analyses of the linearized equations between the present model, the initially-stressed models without pores, the Biot poroelasticity, and the porous hyperelastic model without initial stress are conducted to illustrate the performances of the two ingredients. As a specific example, we investigate the variation of pore sizes under external pressures and initial stresses since changes in pore sizes during deformation are crucial for understanding the accumulation and migration of shale oil and gas. The newly proposed model provides the first initially stressed porous hyperelasticity (ISPH), which is suitable for describing the finite deformation behavior of solid materials with large porosity and significant initial stress simultaneously.

Study the implication of different SiO2/Al2O3 ratios on the pore size and acidity of Beta zeolite and its catalytic pyrolysis mechanism of Kraft lignin

This study employed a one-step synthesis method to prepare Beta zeolites (BZs) with various SiO2/Al2O3 ratios and applied them as catalysts in the process of producing bio-oil from Kraft lignin (KL). The research investigated the changes in acidity and pore size of BZs under different SiO2/Al2O3 ratios and their impact on the catalytic pyrolysis products of KL. Characterization and a series of physicochemical analyses of BZ with different SiO2/Al2O3 ratios as well as catalytic pyrolysis products were carried out. The Pearson correlation coefficient was also used to correlate BZ SiO2/Al2O3 ratios and the acidity/pore size of BZ as well as the distribution of the products and the deoxygenation effect. The results indicate that BZs with different SiO2/Al2O3 ratios can effectively catalyze the upgrading of KL during pyrolysis. BZ with SiO2/Al2O3 ratios of 45 exhibited stronger acidity, a more prominent layered porous structure, and a more orderly distribution of mesopores. It showed the best catalytic upgrading effect on KL, achieving a product yield of 58.4 %. More prominently, the oxygen content is reduced to 14.19 % and the deoxygenation extent of the heavy oil reached 37.1 %.

Impact of PCLNPG Nanopolymeric Additive on the Surface and Structural Properties of PPSU Ultrafiltration Membranes for Enhanced Protein Rejection

This research explored the use of a partially cross-linked graft copolymer (PCLNPG) as an innovative nanopolymer pore-forming agent to enhance polyphenylsulfone (PPSU) membranes for protein separation applications. The study systematically examined the impact of incorporating PCLNPG at varying concentrations on the morphological and surface properties of PPSU membranes. A thorough characterization of the resulting PPSU-PCLNPG membranes was performed, focusing on changes in morphology, water affinity, porosity, pore size, and pore size distribution. The experimental findings demonstrated that the use of PCLNPG led to a significantly more porous structure, as confirmed by SEM analysis, with notable increases in porosity and pore size (nearly double). Additionally, the hydrophilicity of the PPSU membrane was remarkably enhanced. Performance evaluations revealed a substantial improvement in pure water flux, with the flux nearly tripling. The BSA retention was directly correlated with the concentration of the PCLNPG pore former for a loading range of 0.25–0.75 wt.%. The incorporation of PCLNPG also reduced the membrane fouling propensity by reducing both cake layer resistance (Rc) and pore plugging resistance (Rp). These results underscore the potential of PCLNPG-PPSU membranes for wastewater reclamation and nutrient recovery applications.

On the successful pelletization of a fragile mesoporous material and its mechanical stability mechanism

Mechanical stability is a crucial property for the industrial implementation of heterogeneous catalysts and adsorbents. Both particle size and shape need to be investigated for each application where, typically, a compromise between mass transfer and pressure drop needs to be understood. In this study, we investigate the mechanical stability of a fragile mesostructured cellular foam material, formed of 3D aluminosilicate struts and porous cages, that are connected through windows. Successful pelletization was found at ca. 20 MPa, where the structural and textural properties are either unaltered or minimally modified. This condition is satisfactory for the final application of the pelletized material, though a lower-limit pressure could still be optimized. The use of higher pelletization pressures was observed to increase disorder in the systems. The structure contracts, the cage's size decreases markedly leading to more disordered wormhole-like pores. The decrease in cage/pore size seems to compensate for the structural densification, resulting in relatively constant BET areas. The pore volume's decrease is in agreement with the smaller cage sizes and densification. The damage and the mechanism causing this damage differ from that observed in conventional mesoporous materials. Besides the successful pelletization conditions and identification of damage mechanism, it is also noteworthy to highlight that values for BET area can be misleading when assessing mechanical stability; at high pressures, the BET areas remain fairly constant despite significant changes in pore size and structure are observed.

Insights into the pore size distribution of amorphous silica membranes using gas permeation activation energies

Silica-based membranes exhibit significant promise for the separation of hydrogen from other larger gas molecules based on size sieving mechanism, particularly when employed in membrane reactors. Nevertheless, the migration of silanol bonds (Si–OH) formed under hydrothermal conditions leads to alterations in pore size, ultimately compromising the performance of the membrane. Therefore, this study focuses on determining the pore size of cobalt-doped silica membranes before and after hydrothermal treatment by the apparent activation energy of gas permeation. The Oscillator model and the effective medium theory are employed to estimate the potential pore size distribution, as well as to calculate the apparent activation energy and permeability. The calculated apparent activation energy is compared with experimental data to identify the most probable pore size distribution, which showed the minimum activation energy error to the experimental value. The calculated permeability based on the identified pore size distribution is in line with experimental permeability, which validated the identified pore size distribution. Since silica-based membrane is generally applied in hydrothermal conditions, our model successfully identifies the changes in pore size of silica-based membranes after hydrothermal treatment. The results demonstrated that hydrothermal treatment significantly impacts the pore size of silica-based membranes. Specifically, 5-membered rings are prevalent in the intact membrane, but after hydrothermal treatment, there is a gradual shift of the pore size distribution towards larger pores, potentially leading to a decrease in sieving performance. This methodology presents a promising approach for determining intriguing pore size information of porous materials.

The Influence of Calendering Process on the Graphite Anode

Calendering, or pressing, is the final property-defining process for battery electrode manufacturing to maximize the volumetric capacity of the cell through the compaction of an electrode between two large calender rollers12. On one hand, it can reduce the porosity of battery materials thus increase the conductivity of the materials. On the other hand, it can control the thickness of the electrodes, making sure it is uniform and proper thickness to guarantee the minimal variation in the cell thickness, reaching even stack pressure for module assembly and impacting the thermal management [3]. The calendering process significantly influence the performance of lithium-ion battery (LIB).Graphite anode coating on Cu foil was chosen as our baseline coating for this calendering process investigation. The slurry was mixed in a planetary and dispersive mixer and then coated using reverse comma coating method by a scale-up coater with drying zones of 70 °C. Then the coating was calendered by a calendering machine at various conditions.Calendering, though seemingly a simply process, is influenced by several different parameters significantly. In this study, we systematically investigated the calendering process by carrying-out a Design-of-experiment (DOE). The following calendering parameters were investigated: the parameters of calendering machine gap size, calendering pressure, and the speed of the coating web. The calendered graphite coating was then measured for the morphology by scanning electron microscopy (SEM), the pore size change by BET surface area measurement, and Direct current internal resistance (DCIR) by building half cells and cycling and Electrochemical Impedance Spectroscopy (EIS) at 50% State-of-Charge (SOC).The result showed that pressure is the most critical parameter for calendering and the internal resistance and ionic conductivity changes in response to the calendering parameters. The half-cell with calendering at the pressure of 37 MPa, gap size targeted for 30% porosity, the BET surface area around 0.75 m2/g showed highest cell capacity and lowest internal resistance.

Highly Defective Zirconium-Based Metal-Organic Frameworks for the Efficient Adsorption and Detection of Sugar Phosphates in the Biological Sample.

Enrichment and quantification of sugar phosphates (SPx) in biological samples were of great significance in biological medicine. In this work, a series of zirconium-based metal-organic frameworks (MOFs) with different degrees of defects, namely, HP-UiO-66-NH2-X, were synthesized using acetic acid as a modulator and were utilized as high-capacity adsorbents for the adsorption of SPx in biological samples. The results indicated that the addition of acetic acid altered the morphology of HP-UiO-66-NH2-X, with corresponding changes in pore size (3.99-9.28 nm) and specific surface area (894.44-1142.50 m2·g-1). HP-UiO-66-NH2-10 showed the outstanding performance by achieving complete adsorption of all four SPx using only 80 μg of the adsorbent. The excellent adsorption efficiency of HP-UiO-66-NH2-10 was also obtained with a wide pH range and short adsorption time (10 min). Adsorption experiments demonstrated that the adsorption process involved chemical adsorption and multilayer adsorption. By utilizing X-ray photoelectron spectroscopy and density functional theory to explain the adsorption mechanism, it was found that various interactions (including coordination, hydrogen bonding, and electrostatic interactions) collectively contributed to the exceptional adsorption capability of HP-UiO-66-NH2-10. Those results indicated that the defect strategy not only increased the specific surface area and pore size, providing additional adsorption sites, but also reduced the adsorption energy between HP-UiO-66-NH2-10 and SPx. Moreover, HP-UiO-66-NH2-10 showed a low limit of detection (0.001-0.01 ng·mL-1), high precision (<13.77%), and accuracy (80.10-111.83%) in serum, liver, and cells, good stability, high selectivity (SPx/glucose, 1:100 molar ratio), and high adsorption capacity (292 mg·g-1 for SPx). The practical detection of SPx from human serum was also verified, prefiguring the great potentials of defective zirconium-based MOFs for the enrichment and detection of SPx in the biological medicine.

Amphiphilic Polyelectrolyte Complexes for Fouling-Resistant and Easily Tunable Membranes.

Commercial membranes today are manufactured from a handful of membrane materials. While these systems are well-optimized, their capabilities remain constrained by limited chemistries and manufacturing methods available. As a result, membranes cannot address many relevant separations where precise selectivity is needed, especially with complex feeds. This constraint requires the development of novel membrane materials that offer customizable features to provide specific selectivity and durability requirements for each application, enabled by incorporating different functional chemistries into confined nanopores in a scalable process. This study introduces a new class of membrane materials, amphiphilic polyelectrolyte complexes (APECs), comprised of a blend two distinct amphiphilic polyelectrolytes of opposite charge that self-assemble to form a polymer selective layer. When coated on a porous support from a mixture in a nonaqueous solvent, APECs self-assemble to create ionic nanodomains acting as water-conducting nanochannels, enveloped within hydrophobic nanodomains, ensuring structural integrity of the layer in water. Notably, this approach allows precise control over selectivity without compromising pore size, permeability, or fouling resistance. For example, using only one pair of amphiphilic copolymers, sodium sulfate rejections can be varied from >95% to <10% with no change in effective pore size and fouling resistance. Given the wide range of amphiphilic polyelectrolytes (i.e., combinations of different hydrophobic, anionic, and cationic monomers), APECs can create membranes with many diverse chemistries and selectivities. Resultant membranes can potentially address precision separations in many applications, from wastewater treatment to chemical and biological manufacturing.

Mitigation of Volumetric Expansion in Silicon Anodes via Engineered Porosity: Electrochemical Performances and Stress Distribution Implication

To overcome the significant volume expansion issue encountered by traditional silicon anodes in lithium‐ion batteries, this study employs chemical etching techniques to treat aluminum–silicon alloys of various ratios, successfully preparing three types of porous silicon electrode materials with different pore structures. Through a series of electrochemical tests, this article investigates the role of porous silicon structures in improving electrode performance. The results demonstrate that the porous silicon anodes exhibit superior cycle stability and rate capability compared to traditional solid silicon anodes. This confirms the effectiveness of the porous structure in mitigating the significant volume expansion during the charge and discharge process of silicon materials and in preventing premature electrode failure, thereby significantly enhancing the electrode's cycle life. Remarkably, the porous silicon with a high porosity rate shows exceptionally outstanding performance. Additionally, using computer simulations, this study also models the impact of changes in pore size within the porous silicon material at different states of charge and discharge on the stress distribution at the particle center and surface. These experimental and simulation results jointly provide strong empirical evidence for applying porous silicon materials as high‐performance anode materials for lithium‐ion batteries and offer essential guidance for future stress analysis and electrode design of porous silicon electrode materials.

Alginate-Sr/Mg Containing Bioactive Glass Scaffolds: The Characterization of a New 3D Composite for Bone Tissue Engineering.

In bone regeneration, combining natural polymer-based scaffolds with Bioactive Glasses (BGs) is an attractive strategy to improve the mechanical properties of the structure, as well as its bioactivity and regenerative potential. Methods: For this purpose, a well-studied alginate/hydroxyapatite (Alg/HAp) porous scaffold was enhanced with an experimental bioglass (BGMS10), characterized by a high crystallization temperature and containing therapeutic ions such as strontium and magnesium. This resulted in an improved biological response compared to 45S5 Bioglass®, the "gold" standard among BGs. Porous composite scaffolds were fabricated by freeze-drying technique and characterized by scanning electron microscopy and microanalysis, infrared spectroscopy, and microcomputed tomography. The mechanical properties and cytocompatibility of the new scaffold composition were also evaluated. The addition of bioglass to the Alg/HAp network resulted in a slightly lower porosity. However, despite the change in pore size, the MG-63 cells were able to better adhere and proliferate when cultured for one week on a BG scaffold compared to the control Alg/HAp scaffolds. Thus, our findings indicate that the combination of bioactive glass BGMS10 does not affect the structural and physicochemical properties of the Alg/HAp scaffold and confers bioactive properties to the structures, making the Alg/HAp-BGMS10 scaffold a promising candidate for future application in bone tissue regeneration.

Microstructure and damage characteristics of cement mortar with different aggregate sizes after cooling based on nuclear magnetic resonance technology

This article studies the effects of cooling methods and aggregate sizes (particle size: 0.63–1.25 mm, 1.25–2.5 mm, 2.5–5.0 mm, 5.0–10.0 mm) on the microscopic properties and damage characteristics of cement mortar specimens. After heating the specimens to 400 °C, air cooling (cooling in air as a whole, A), water cooling (cooling in water as a whole, W), and semi-water cooling (half in air and the other half in water, AW) cooling methods are applied. The T2 spectrum, magnetic resonance imaging (MRI), permeability and P-wave velocity of the specimens were tested by low-field nuclear magnetic resonance (NMR), pulse pore permeability tester and digital acoustic wave instrument, respectively. The effect of cooling method and aggregate size on pore size distribution and fractal characteristics, permeability and tortuosity, P wave and damage degree of cement mortar specimens were studied. The relationship between MRI pixel value and damage degree was deeply explored. The results show that the average permeability and MRI pixel value increase after high temperature, and the pore tortuosity decreases. The mass loss rate, the increase of the most probable pore size and the increase of the pore volume are negatively correlated with the aggregate size, and the permeability ratio, the decrease of the tortuosity and the damage degree are positively correlated with the aggregate size. At the same time, the influence of cooling method on mass loss rate, porosity and permeability from large to small is: A, AW, W, while the decrease rate of pore tortuosity from large to small is: AW, W, A. The most probable pore size and pore volume change most obviously after high temperature treatment of W and AW. In addition, with the increase of aggregate size, the fractal dimension increases under air cooling, and the U-shaped change with W2.5 particle size as the threshold decreases first and then increases under semi-water cooling. Finally, there is a good exponential relationship between the average ratio of MRI pixel values and the damage degree, and the damage degree of the sample can be obtained by the average ratio of MRI pixel values.

Competitive transport and adsorption of CO2/H2O in the graphene nano-slit pore: A molecular dynamics simulation study

The study of pore structure, surface sites, and the competitive adsorption and mass transfer of CO2, particularly in conjunction with H2O, in porous solid materials is crucial for developing CO2 capture materials with superior performance and achieving carbon emission reduction goals. This paper presents the development and investigation of amino-modified graphene lamellae pore models using standard number of particles, volume, and temperature system integrated molecular dynamics simulations in a non-equilibrium state. The findings reveal that CO2 adsorption on the pore surface of graphene lamellae occurs in a two-layered manner, influenced by van der Waals and electrostatic forces. The adsorption capacity of the initial layer at a constant temperature is contingent upon the material’s adsorption area, while the site density determines the second layer’s adsorption capacity. Increasing the site density from 0/Å2 to 0.008/Å2 enhances the number of CO2 molecules in the second layer by approximately 35.6 %, though it significantly reduces their diffusion rate. Additionally, changes in temperature and pore size predominantly affect the diffusion rate and CO2 adsorption capacity. The study also explores the competitive adsorption dynamics of H2O molecules with CO2 in the pore channels. It was observed that at low temperatures, H2O molecules predominantly undergo surface diffusion, occupying the pore channel surfaces and thus impacting CO2 adsorption. At a CO2:H2O ratio of 1:1, H2O molecules cover 54.1 % of the adsorption area and may form clusters that obstruct the pore channels, thereby hindering CO2 diffusion. Calculations of surface diffusion rates for H2O molecular clusters at various CO2/H2O ratios indicate that smaller clusters exhibit higher diffusion rates. The computational approach employed in this study demands minimal resources and enables swift calculations, offering a new theoretical model for optimizing adsorbent design, enhancing CO2 capture efficiency, and exploring novel adsorbent materials.

СТРУКТУРА ПОР ЯЧЕИСТОГО БЕТОНА С ОТХОДАМИ СТЕКЛОБОЯ ЭЛЕКТРОННО-ЛУЧЕВЫХ ТРУБОК

To date, the issue of handling toxic unsorted waste of cathode ray tubes (CRT) glass cullet remains relevant. The present paper proposes to replace part of the fine aggregate of cellular concrete intended for sound, heat or radiation protection with CRT glass waste heat-treated in the presence of a sodium hydroxide solution. The purpose of the research is to study the structure formation of the cellular concrete pores in case of replacement of part of the aggregate. The microscopy of the samples fracture was studied both visually and using software that made it possible to estimate the pore size when convert-ing the image to the relief mode. The study showed that the aggregate replacement results not only in quantitative changes in pore size, but also in qualitative changes related to the mechanism of the pore structure formation. Thus, when adding unsorted waste heat-treated in an alkaline environment, with a particle diameter of no more than 630 μm, there was a decrease in pore size and a decrease in size distribution compared with the reference sample. The changes are caused by structure formation, which can be divided into two stages - the formation of conglomerates and their swelling. With a decrease in the diameter of the part of the waste of a maximum size of 90 μm, a decrease in the pore size was recorded compared to the reference value, but due to the concrete skeleton formation before the end of gas development, destruction of the pore walls was observed.

Flexible-Rigid Aluminum-Organic frameworks with Ultra-Fine Pore-Environment regulation for benchmark acetylene storage and purification

Rational regulation of functional groups on the pore surface of robust aluminum metal–organic framework (CAU-10-H) from amino (–NH2), hydrazino (–N2H3), to azido (–N3) continuously control their framework rigidity-flexibility together with ultra-fine pore-size change in the scale of 0.1–0.5 Å. Benefited from the rigid architecture and suitable pore environments, CAU-10-NH2 exhibits a supreme acetylene (C2H2) storage density (473 g/L) exceeding the values of liquid C2H2 (393 g/L) and all reported MOF adsorbents under ambient conditions. Different from CAU-10-H/NH2/N2H3, CAU-10-N3 exhibited temperature-dependent flexible stepwise adsorption behaviors for C2H2 with azido groups as the guest-sensitive gate, having highest storage capacity (106 cm3 cm−3) and second-high storage density (405 g/L) among these materials. Notably, compared with other C2-hydrocarbon and CO2 molecules, only C2H2 can open the azido door at 298 K, and thus effectively enhancing their separation selectivity with top-level uptake ratios for C2H2/C2H4 (2.65) and C2H2/CO2 (2.93), which are further supported by the practical fixed-bed breakthrough curves and theoretical simulations. Such a rational combination of rigidity and flexibility breaks new ground in MOF chemistry and sets a benchmark for acetylene storage and purification.

Dissipative Particle Dynamics Study on the Phase Region of Spatial Gradient Materials Produced by Photoinduced Isomerization

AbstractSpatial gradient materials occupy an important research position in the field of functional materials with their unique porous structure. Gradient changes in pore size and density distribution have received extensive attention in the fields of biomimetic and smart materials. The gradient transition law is mathematically related to the driving force of isomerization reaction and component phase separation. In this study, a dissipative particle dynamics simulation is used to introduce photoisomerization reactions into the system. Lambert's law is used to construct a reaction model for the variation of light intensity with irradiation depth, and a gradient structure with a spatial transition law is obtained. The effects of the extinction coefficient ε, the initial reaction probability Pr0, and the interactions α(A,B) between the isomerized molecules as well as the viscosity on the formation of the gradient structure are investigated in detail. Furthermore, the mathematical proportionality between the size of the phase region and interfacial energy of the two phases is elucidated. This study provides preliminary computational insights into the factors affecting the photoinduced phase separation process of polymeric gradient materials. It may help to develop effective strategies to improve the phase separation and properties of polymer gradient materials in subsequent studies.