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Water ubiquitously exists with dissolved salt in both natural and engineered porous media, such as soil, rock, concrete, and tissue; therefore, its freezing temperature depression behavior is of particular interest to various scientific communities tackling with mechanics and physics of porous media. To date, it remains elusive which physical mechanism accounts for its freezing temperature depression and how dissolved ions affect it. Herein, a series of pore-scale experiments were designated to investigate the freezing temperature of salt solutions in tubes with varying pore diameters, pore solution volumes, solid–liquid interfacial areas, ion concentrations, and ion types. The results reveal two main findings: (i) the freezing temperature depression of pore solutions is governed by the heterogeneous ice nucleation (HIN) at the water–solid interface, as evidenced by the observation that the freezing temperature decreases with the decreasing solid–liquid interfacial areas, regardless of pore diameter and pore solution volume; (ii) the dissolved salts alter HIN processes via changing the osmotic potential across the ice embryo–liquid water interface, as indicated by the observation that the freezing temperature is mainly determined by the salt concentration irrespective of salt types. Furthermore, the classical nucleation theory model is adapted for the freezing behavior of pore solutions by including an osmotic potential term. The model shows excellent performance in capturing experimental data with various pore solution concentrations, further substantiating the HIN as the physical mechanism governing pore solution freezing. [ABSTRACT FROM AUTHOR]

Electro-osmotic flow (EOF) is a phenomenon where fluid motion occurs in porous materials or micro/nano-channels when an external electric field is applied. In the particular example of single-molecule electrophoresis using single nanopores, the role of EOF on the translocation velocity of the analyte molecule through the nanopore is not fully understood. The complexity arises from a combination of effects from hydrodynamics in restricted environments, electrostatics emanating from charge decorations and geometry of the pores. We address this fundamental issue using the Poisson–Nernst–Planck and Navier–Stokes (PNP–NS) equations for cylindrical solid-state nanopores and three representative protein nanopores (α-hemolysin, MspA, and CsgG). We present the velocity profiles inside the nanopores as a function of charge decoration and geometry of the pore and applied electric field. We report several unexpected results: (a) The apparent charges of the protein nanopores are different from their net charge and the surface charge of the whole protein geometry, and the net charge of inner surface is consistent with the apparent charge. (b) The fluid velocity depends non-monotonically on voltage. The three protein nanopores exhibit unique EOF and velocity–voltage relations, which cannot be simply deduced from their net charge. Furthermore, effective point mutations can significantly change both the direction and the magnitude of EOF. The present computational analysis offers an opportunity to further understand the origins of the speed of transport of charged macromolecules in restricted space and to design desirable nanopores for tuning the speed of macromolecules through nanopores. [ABSTRACT FROM AUTHOR]

In this work, we implemented an off-axis digital holographic microscopy (DHM) setup to study the behavior of liquid drops on nanostructured porous silicon (PS) membranes. When a liquid comes into contact with the PS structure, capillary action and surface tension give rise to imbibition of the liquid into the intricate volume of the pores. At the same time, the vapor field developed around the drop enhances liquid condensation and evaporation into and from the pores. The complex interplay between these phenomena (capillary driven internal flows, condensation, and evaporation) is not yet fully understood but the methods we propose can provide new insights. We demonstrate how DHM allows determining the filling fraction of the porous membrane around drying drops of water and isobutyl alcohol. The phase information obtained from registered holograms provides quantitative information that permits to reconstruct the filling fraction along the porous membrane and its evolution during the drying process. Additionally, relevant parameters such as speed and contact angle during retraction of the drops can be measured. These methods can be further extended to other porous materials, such as porous alumina, micro- and macro-PS, to develop better fluid-dynamic models for describing fluid behavior in highly confined structures. [ABSTRACT FROM AUTHOR]

Electromagnetohydrodynamic (EMHD) flow in porous media is recently gaining substantial attention from researchers. EMHD involves analyzing the combined effects of electric and magnetic fields on the behavior of fluid flow through a medium. The effective permeability of porous materials is of great interest for many environmental and industrial applications. The present study focuses on the modeling of single-phase fluid flow in porous media under combined effects of electric and magnetic fields at the pore scale by employing a two-scale computational homogenization technique. The primary objective of this study is to establish a definition of "electromagnetopermeability" that accurately characterizes the effective permeability of a porous medium under the EMHD effects. Additionally, the study investigates the impact of wall zeta potential, Debye length, and the intensity of external magnetic and electric fields, represented by the Hartmann number and the non-dimensional parameter S, respectively, on the electromagnetopermeability tensor within an idealized three-dimensional periodic porous domain. It is observed that the EM-permeability is significantly affected by the existence of the flow-assisting and flow-opposing components of the Lorentz force term in the momentum equation. The implications of this research extend to several industries, including geology, medicine, chemistry, and energy conversion. [ABSTRACT FROM AUTHOR]

In this article, the phenomenon of countercurrent imbibition in a specific displacement method occurs within a dipping homogeneous porous medium. This phenomenon plays a vital role in the process of oil recovery, which motivates our analysis. To overcome the difficulties associated with the nonlinear partial differential equation governing the countercurrent imbibition phenomenon, we have been using two distinct methods: the natural transform decomposition method and the variational iteration transform method with their convergence analysis for solutions. These techniques give different perspectives and enable us to obtain approximate solutions. Notably, both the proposed methods demonstrate the potential for substantial production of oil during the secondary oil recovery process in the petroleum industry. The obtained results by the proposed methods show the efficiency in optimizing the oil recovery rate. [ABSTRACT FROM AUTHOR]

A healthy breath is mainly composed of water, carbon dioxide, molecular nitrogen, and oxygen and it contains many species, in small quantities, which are related to the ambient atmosphere and the metabolism. The breath of a person affected by lung cancer presents a concentration of 1-propanol higher than usual. In this context, the development of specific sensors to detect 1-propanol from breath is of high interest. The amount of propanol usually detected on the breath is of few ppb; this small quantity is a handicap for a reliable diagnostic. This limitation can be overcome if the sensor is equipped with a pre-concentrator. Our studies aim to provide an efficient material playing this role. This will contribute to the development of reliable and easy to use lung cancer detectors. For this, we investigate the properties of a few hydrophobic porous materials (chabazite, silicalite-1, and dealuminated faujasite). Hydrophobic structures are used to avoid saturation of materials by the water present in the exhaled breath. Our experimental and simulation results suggest that silicalite −1 (MFI) is the most suitable structure to be used as a pre-concentrator. [ABSTRACT FROM AUTHOR]

Nanoporous materials are of great interest in many applications, such as catalysis, separation, and energy storage. The performance of these materials is closely related to their pore sizes, which are inefficient to determine through the conventional measurement of gas adsorption isotherms. Nuclear magnetic resonance (NMR) relaxometry has emerged as a technique highly sensitive to porosity in such materials. Nonetheless, streamlined methods to estimate pore size from NMR relaxometry remain elusive. Previous attempts have been hindered by inverting a time domain signal to relaxation rate distribution, and dealing with resulting parameters that vary in number, location, and magnitude. Here we invoke well-established machine learning techniques to directly correlate time domain signals to BET surface areas for a set of metal-organic frameworks (MOFs) imbibed with solvent at varied concentrations. We employ this series of MOFs to establish a correlation between NMR signal and surface area via partial least squares (PLS), following screening with principal component analysis, and apply the PLS model to predict surface area of various nanoporous materials. This approach offers a high-throughput, non-destructive way to assess porosity in c.a. one minute. We anticipate this work will contribute to the development of new materials with optimized pore sizes for various applications.

Hydrophobicity has proven fundamental in an inexhaustible amount of everyday applications. Material hydrophobicity is determined by chemical composition and geometrical characteristics of its macroscopic surface. Surface roughness or texturing enhances intrinsic hydrophilic or hydrophobic characteristics of a material. Here we consider crystalline surfaces presenting molecular-scale texturing typical of crystalline porous materials, e.g., metal-organic frameworks. In particular, we investigate one such material with remarkable hydrophobic qualities, ZIF-8. We show that ZIF-8 hydrophobicity is driven not only by its chemical composition but also its sub-nanoscale surface corrugations, a physical enhancement rare amongst hydrophobes. Studying ZIF-8's hydrophobic properties is challenging as experimentally it is difficult to distinguish between the materials' and the macroscopic corrugations' contributions to the hydrophobicity. The computational contact angle determination is also difficult as the standard "geometric" technique of liquid nanodroplet deposition is prone to many artifacts. Here, we characterise ZIF-8 hydrophobicity via: (i) the "geometric" approach and (ii) the "energetic" method, utilising the Young–Dupré formula and computationally determining the liquid–solid adhesion energy. Both approaches reveal nanoscale Wenzel-like bathing of the corrugated surface. Moreover, we illustrate the importance of surface linker termination in ZIF-8 hydrophobicity, which reduces when varied from sp3 N to sp2 N termination. We also consider halogenated analogues of the methyl-imidazole linker, which promote the transition from nanoWenzel-like to nanoCassie–Baxter-like states, further enhancing surface hydrophobicity. Present results reveal the complex interface physics and chemistry between water and complex porous, molecular crystalline surfaces, providing a hint to tune their hydrophobicity. [ABSTRACT FROM AUTHOR]

We numerically examine the driven transport of an overdamped self-propelled particle through a two-dimensional array of circular obstacles. A detailed analysis of transport quantifiers (mobility and diffusivity) has been performed for two types of channels, channel I and channel II, that respectively correspond to the parallel and diagonal drives with respect to the array axis. Our simulation results show that the signatures of pinning actions and depinning processes in the array of obstacles are manifested through excess diffusion peaks or sudden drops in diffusivity, and abrupt jumps in mobility with varying amplitude of the drive. The underlying depinning mechanisms and the associated threshold driving strength largely depend on the persistent length of self-propulsion. For low driving strength, both diffusivity and mobility are noticeably suppressed by the array of obstacles, irrespective of the self-propulsion parameters and direction of the drive. When self-propulsion length is larger than a channel compartment size, transport quantifiers are insensitive to the rotational relaxation time. Transport with diagonal drives features self-propulsion-dependent negative differential mobility. The amplitude of the negative differential mobility of an active particle is much larger than that of a passive one. The present analysis aims at understanding the driven transport of active species like, bacteria, virus, Janus particle etc. in porous medium. [ABSTRACT FROM AUTHOR]

Investigating thermal convection within porous media permeated by fluids and micro-organisms stands as a significant inquiry with broad relevance across geophysical and engineering domains. Studying convection within porous media can aid in controlling temperature and nutrient distribution for cell growth and tissue regeneration, as well as the efficiency of biofuel fermentation and production processes. Hence, the primary objective of this study is to investigate the influence of time-periodic gravitational forces on Darcy–Brinkman bio-thermal convection within a porous medium layer. This medium is saturated with a Newtonian fluid that encompasses gyrotactic micro-organisms. The gravity modulation amplitude is assumed to be very small. A weak nonlinear stability analysis is performed to analyze the stationary mode of bioconvection. The heat transport, measured by the Nusselt number, is governed by a non-autonomous Ginzburg–Landau equation. The research explores the influence of several parameters on heat transport, including the Vadaszs number, the modified bioconvective Rayleigh–Darcy number, cell eccentricity, modulation frequency, and modulation amplitude. The results are presented graphically, illustrating the impact of these parameters on heat transfer. The findings reveal that both the Vadaszs number and the modulation amplitude have a positive effect on heat transfer, enhancing the process. On the other hand, an increase in the modified bioconvection Rayleigh–Darcy number and cell eccentricity leads to a decrease in heat transfer. Furthermore, a comparison between the modulated and unmodulated systems indicates that the modulated systems have a more significant influence on the stability problem compared to the unmodulated systems. This highlights the effectiveness of external modulation in controlling heat transport within the system. [ABSTRACT FROM AUTHOR]

Heterogenous materials under shock compression can be expected to reach different shock states throughout the material according to local differences in microstructure and the history of wave propagation. Here, a compact, multiple-beam focusing optic assembly is used with high-speed velocimetry to interrogate the shock response of porous tantalum films prepared through thermal-spray deposition. The distribution of particle velocities across a shocked interface is compared to results obtained using a set of defocused interferometric beams that sampled the shock response over larger areas. The two methods produced velocity distributions along the shock plateau with the same mean, while a larger variance was measured with narrower beams. The finding was replicated using three-dimensional, mesoscopically resolved hydrodynamics simulations of solid tantalum with a pore structure mimicking statistical attributes of the material and accounting for radial divergence of the beams, with agreement across several impact velocities. Accounting for pore morphology in the simulations was found to be necessary for replicating the rise time of the shock plateau. The validated simulations were then used to show that while the average velocity along the shock plateau could be determined accurately with only a few interferometric beams, accurately determining the width of the velocity distribution, which here was approximately Gaussian, required a beam dimension much smaller than the spatial correlation lengthscale of the velocity field, here by a factor of ∼30×, with implications for the study of other porous materials. [ABSTRACT FROM AUTHOR]

In this work, expanding cylinder experiments are performed using a gas gun on the aluminum 6061 alloy to understand the dynamic deformation and failure behavior of this material in the presence of surface defects in the form of scratches. The experiments are then modeled with the modified Tepla (for tensile plasticity) model, which is equipped with the damage yield function of Gurson ["Continuum theory of ductile rupture by void nucleation and growth: Part I—Yield criteria and flow rules for porous ductile media," (1977)] and Tvergaard and Needleman [Acta Metall. 32(1), 157–169 (1984)], over-stress viscosity [F. Addessio and J. Johnson, J. Appl. Phys. 74(3), 1640–1648 (1993)], and the underlying viscoplastic model of Preston et al. [J. Appl. Phys. 93(1), 211–220 (2003)] (Preston–Tonks–Wallace model) for the dense material. The Tepla model parameters were calibrated using the Bayesian approach against experimentally measured free-surface velocity data obtained from plate impact experiments on the aluminum 6061 alloy. The evolution of radial expansion and shapes of the deformed cylinder from the simulations on a pristine cylinder wall and a cylinder wall with a longitudinal surface defect shows excellent agreement with the corresponding experimental results. Finally, the role of surface defect size and cylinder wall geometry on the dynamic strength of the cylinder wall was also investigated through a series of simulations. [ABSTRACT FROM AUTHOR]

Real-time monitoring and quantitative measurement of molecular exchange between different microdomains are useful to characterize the local dynamics in porous media and biomedical applications of magnetic resonance. Diffusion exchange spectroscopy (DEXSY) is a noninvasive technique for such measurements. However, its application is largely limited by the involved long acquisition time and complex parameter estimation. In this study, we introduce a physics-guided deep neural network that accelerates DEXSY acquisition in a data-driven manner. The proposed method combines sampling pattern optimization and physical parameter estimation into a unified framework. Comprehensive simulations and experiments based on a two-site exchange system are conducted to demonstrate this new sampling optimization method in terms of accuracy, repeatability, and efficiency. This general framework can be adapted for other molecular exchange magnetic resonance measurements. [ABSTRACT FROM AUTHOR]

To understand the dynamical and conformational properties of deformable active agents in porous media, we computationally investigate the dynamics of linear chains and rings made of active Brownian monomers. In porous media, flexible linear chains and rings always migrate smoothly and undergo activity-induced swelling. However, semiflexible linear chains though navigate smoothly, shrink at lower activities, followed by swelling at higher activities, while semiflexible rings exhibit a contrasting behavior. Semiflexible rings shrink, get trapped at lower activities, and escape at higher activities. This demonstrates how activity and topology interplay and control the structure and dynamics of linear chains and rings in porous media. We envision that our study will shed light on understanding the mode of transport of shape-changing active agents in porous media. [ABSTRACT FROM AUTHOR]

The theoretical investigation of gas adsorption, storage, separation, diffusion, and related transport processes in porous materials relies on a detailed knowledge of the potential energy surface of molecules in a stationary environment. In this article, a new algorithm is presented, specifically developed for gas transport phenomena, which allows for a highly cost-effective determination of molecular potential energy surfaces. It is based on a symmetry-enhanced version of Gaussian process regression with embedded gradient information and employs an active learning strategy to keep the number of single point evaluations as low as possible. The performance of the algorithm is tested for a selection of gas sieving scenarios on porous, N-functionalized graphene and for the intermolecular interaction of CH4 and N2. [ABSTRACT FROM AUTHOR]

Mechanical stability of freeze-casted porous alumina can be achieved by the stimulation of densification with control of the grain growth during sintering. To tailor the porous microstructure beneficially, in this study TiO2 was added and its segregation effect on the densification and its grain growth behaviors were investigated. As a result, abnormal grain growth was observed with faceted interfaces and explained by grain boundary structure dependent grain growth theory. In terms of densification, a higher bulk density was obtained with the addition of 1.5 wt% TiO2 (41.76 %TD) compared to that without doping (36.02 %TD). The benefit was evident at 1400 °C, whereas the bulk density decreased even with an addition of TiO2 above 1500 °C. This temperature dependence could be understood by a change in the dominant densification mechanism at 1500 °C, solving the puzzle of the enhanced densification only at low temperature.

Abstract Sulfur polymers produced through 'inverse vulcanization' exhibit various attributes, such as photocatalytic activity and a high capacity to adsorb heavy metals. Nevertheless, there is a lack of research investigating the use of sulfur polymers as materials for the removal of organic contaminants. In this work, porous sulfur polymers (PSPs) were synthesized from elemental sulfur and 1,3-diisopropenylbenzene, with porosity introduced via salt templating. The result is a material that can strongly adsorb and chemically neutralize a model organic contaminant (caffeine). PSPs show adsorption up to 5 times higher than a leading adsorption material (activated carbon). Furthermore, either the adsorption or degradation processes can govern the removal efficiency depending on the synthesis parameters of PSPs. This is the first-ever report demonstrating sulfur polymers as effective materials for removing emerging contaminants from water. The versatile synthesis of sulfur polymers offers variation, which means that there is much more to explore in this exciting research area.

Effects of adding microcrystalline cellulose (MCC) and cellulose nanocrystals (CNC) were evaluated relative to the mechanical, thermal, morphological, and structural properties of rigid polyurethanes (rPUs). The composites were prepared with the blending of polyols/isocyanates and the cellulosic fillers at 0.25%, 0.5%, and 1% loadings. Scanning electron microscopic images showed that the samples had micro-scaled porosity, with cell sizes ranging from 250 to 800 nm. The fillers improved the mechanical strengths and modulus of neat rPUs due to the presence of the nano-sized cells in rPUs matrix. The addition of both fillers generally did not provide a positive effect on the thermal properties, and the weight loss generally increased while the loading rate of the fillers was increased from 0.25% to 1%. The samples had two small crystalline peaks at 18° and 19° according to the X-ray diffraction analysis. From the results, it can be said that the presence of both fillers generally improved all properties of the neat rPUs, and the effects of CNC on the properties were higher than MCC due to both lower particle size and the higher crystallinity of CNC.

Dedicated coating materials for anechoism and furtivity in underwater acoustics must exhibit a strong reliability regarding their mechanical resistance to hydrostatic pressure. Soft porous materials, especially, a distribution of soft porous beads within a polyurethane matrix, have been previously proposed as an acoustic insulator device. The purpose of the present letter is to investigate the attenuation efficiency of soft porous silicone beads-based materials while being exposed to uniaxial loads mimicking hydrostatic pressures encountered in underwater acoustics. The acoustic performance of this locally resonant material is then compared to the classical coating technology using micro-balloons. The use of an adapted surfactant (a silicone alkyl polyether compound) in the fabrication process of the soft porous silicone-based beads, obtained through an emulsion templating process, leads to particles exhibiting an open porosity. The (resonant) attenuation of the soft porous beads-based material remains greater than the micro-balloons-based material until several bars. Above this critical resilience value, the mechanical stress irreversibly damages the soft porous beads. [ABSTRACT FROM AUTHOR]

The combined heat and mass transfer, the so-called thermosolutal convective problem, has become an attractive field of research in many diversified areas. In this paper, for the first time, oscillatory flow analysis has been carried out for triple diffusive viscoelastic fluid flow in a porous medium. A comprehensive model is developed for the modified Darcy–Brinkman–Oldroyd-B fluid, porous medium, Boussinesq approximation, heat and mass transfer across a finite temperature and concentration difference in the chemical potential of two salts. Triple diffusive viscoelastic fluid flows through porous media have grown significantly as this situation occurs in more than a few applications such as improved oil recovery filtration, liquid complex molding, solidification of liquid crystals, cooling of metallic plate in a bath, exotic lubricants and colloidal solutions, polymer processing, chemical and bioengineering industries, among others. The governing coupled nonlinear partial differential equations with boundary constraints represent the modeled flow problem. In addition, these equations are converted into non-dimensional form by employing suitable non-dimensionalizing quantities. The impacts of the pertinent parameters and related dimensionless numbers on the dimensionless velocity, temperature, concentrations, shear stress, heat and mass transfer are examined for both suction and injection cases. It has been found that when the injection level on the heated plate is increased, the shear rate increases for each channel plate. Furthermore, we recognized that the viscoelastic parameters exhibit an opposite kind of behavior on the velocity, temperature, and concentrations fields. [ABSTRACT FROM AUTHOR]

This work introduces a novel isogeometric method for addressing steady, saturated groundwater flow as a free-boundary problem. The innovation lies in adopting a double spline parameterization technique for accurately representing both the porous medium and the fully saturated zone. To linearise the governing equation, we differentiate them with respect to the coefficients of the geometric parameterization. This process results in a quasi-Newton method. Several benchmark numerical tests demonstrate the applicability and effectiveness of the proposed technique. [ABSTRACT FROM AUTHOR]

A numerical model was used to simulate natural convection heat transfer in a two-dimensional square enclosure filled with nanofluid and saturated with porous media. The enclosure contained three heated tubes with Rayleigh numbers (Ra) ranging from 102 to 3 × 104. The governing equations with Boussinesq approximation for natural convection were solved iteratively using the finite volume technique through ANSYS FLUENT-CFD commercial package. The Darcy–Forchheimer–Brinkman and Local Thermal Equilibrium models were applied for water and nanofluid flow across the porous zone. The numerical analysis was executed systematically for significant parameters that have a substantial impact on natural convection heat transfer, namely, aspect ratio (AR = 1.25 − 3.75), nanoparticle volume fraction (Φ = 0.25%, 0.5%, 0.7% and 1%), and the porosity of metal foam (ε = 0.3, 0.4, 0.5, 0.6 and 0.7). The aspect ratio was found to have a considerable impact on the averaged Nusselt number (Nuave). For AR = 3.75, the value of Nuave for all Rayleigh numbers increased by approximately 5.22 times compared to AR = 1.25. Moreover, Nuave remained approximately constant as the concentration of alumina-water nanofluid increased from 0.25% to 1%. The novelty of this study lies in the multi-objective optimal design approach adopted by adopting DX-12 with the outcomes of ANSYS FLUENT-CFD. The averaged Nusselt number and convection heat transfer rate reached their optimal values by nearly 13 and 9 times, respectively, at the lowest possible porosity (ε = 0.3), the lowest possible nanofluid concentration (Φ = 0), and the highest possible aspect ratio value (AR = 3.75). [ABSTRACT FROM AUTHOR]

This study investigates the steady, incompressible MHD flow of a hybrid nanofluid over a vertical solid cone embedded in a porous medium under suction effect. The research explores the effects of various factors, such as thermal radiation, chemical reactions, heat generation, viscous dissipation, and Joule heating on heat and mass transfer phenomena. To investigate the effects of hybrid nanoparticles, we consider single-walled carbon nanotubes (SWCNT) and alumina (Al2O3) along with water (H2O) as the base fluid. After a suitable similarity transformation, the governing equations are reconstructed and solved using the Keller-box numerical scheme. We present graphical and tabular analyses of various parameter impacts on heat transfer profiles and coefficients. This study provides valuable insights into the control of fluid dynamics and heat transfer in porous media, which have significant implications for industrial and engineering applications. The findings of the current article are in excellent agreement with previously published works. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel type of PILs has been fabricated. • PILs integrate the permanent pores of porous solids with the exceptional properties of ILs. • PILs possess high activity and selectivity for the DBT oxidation. • IL moiety serves as an extractant to enrich DBT and creates an electrostatic solvent effect. • UiO-66 moiety serves as a catalysis to handily catalyze the ODS reaction. Developing a highly efficient strategy for the stabilization of the solid-liquid interface is a persistent pursuit for researchers. Herein, porous ionic liquids based on UiO-66 (Zr) porous materials were synthesized and applied to the selective desulfurization catalysis, which integrates the permanent pores of porous solids with the exceptional properties of ionic liquids. Results show that porous ionic liquids possess high activity and selectivity for dibenzothiophene. Experimental analysis and density functional theory calculations revealed that the ionic liquids moiety served as an extractant to enrich dibenzothiophene into the porous ionic liquids phase through the π···π and C H···π interactions. Additionally, the electrostatic solvent effect in the porous ionic liquids contributes to the stabilization solid-liquid interface, which was favorable for UiO-66 moiety to catalytically activate hydrogen peroxide (H 2 O 2) to generate ·OH radicals, and subsequently oxidized dibenzothiophene to the corresponding sulfone. It is hoped that the development of porous ionic liquids could pave a new route to the stabilization of the solid-liquid interface for catalytic oxidation. [ABSTRACT FROM AUTHOR]

Silicon is a promising anode material in lithium‐ion batteries (LIBs) for its ultra‐high theoretical capacity; however, its large volume expansion and low electrical conductivity trigger capacity degradation and poor stability. Herein, an ultra‐low 4.3 wt% Si‐doped porous MoC (p‐Si@MoC) is constructed by a facile thermal reduction on a core‐shelled precursor of ZnMo‐hybrid zeolitic imidazole framework (HZIF‐ZnMo) coated by tetraethyl orthosilicate (TEOS), delivering a high capacity and superior cycling stability (976.6 mAh g−1 after 250 cycles at 0.2 A g−1) in LIBs. The homogeneous distribution in the porous MoC matrix contributes to its maximum capacity utilization. Meanwhile, the porous substrate enhances Li ion transport kinetics and reduced the volume expansion of Si. The excellent electronic conductivity of p‐Si@MoC is revealed by the density functional theory (DFT) calculations. The Mo─Si bonds formed by Si‐doped in the MoC matrix are verified by X‐ray absorption near‐edge structure (XANES) and extended X‐ray absorption fine structure (EXAFS). Moreover, the in situ X‐ray diffraction (in situ XRD) reveals the lithium storage mechanism. This work presents an excellent structural design and synthesis strategy for high‐performance silicon‐based anode materials. [ABSTRACT FROM AUTHOR]

Crystalline porous organic polymers (CPPs) or covalent organic frameworks (COFs), are composed by light elements linked by covalent bonds. Despite the remarkable progress attained, there are still bottlenecks limiting further development, some of them related to the presence of defects during their synthesis as well as in‐depth understanding of structure of active centers and/or details of the reaction mechanism. Indeed, very often the proposed structures are far from reality because defects and disorders have not been considered. The present review provides an illustrative overview of "defects and disorder in COFs". These defects include those not only generated during the synthesis and manipulation of COFs, but also lack of crystallinity, stacking disorder and network vacancies. The review starts giving general remarks on organic COFs and their synthetic methods, followed by different methods to play and manage defects, how to minimize them or how to take advantage of them to gain new properties and applications. Selected characterization techniques to quantify defective structures and active sites in COFs are also presented. Finally, the challenges and future opportunities in the field have been summarized in the last section. [ABSTRACT FROM AUTHOR]

Powder‐based piezo‐catalysis, as an effective approach to degrade wastewater and produce hydrogen from water splitting, has been widely used in the field of energy conservation and pollution reduction. However, these hard‐to‐recycle powders pose a challenge of secondary pollution in the environment. As a result, this paper provides an alternative strategy based on the manufacture of porous ceramics as a green chemistry approach to replace ferroelectric powders currently used in traditional piezo‐catalysis. The piezo‐catalytic properties of Ba0.75Sr0.25TiO3 (BST) ceramics prepared using freeze casting and direct ink writing techniques are investigated in detail. The positive effect of introducing micro‐ and macro‐pores is explored and discovered, where a BST ceramic with hierarchical pore channels is prepared by a combination of direct ink writing and freeze casting and exhibts the highest first‐order kinetic rate constant per mass of catalysts, k, of up to 2.91 min−1 kg−1 compared to bulk BST ceramics. This study therefore provides the first report for the benefits of hierarchical porous ferroelectric ceramics used in water splitting, with an average H2 production rate reaching 848.88 nmol g−1 h−1. [ABSTRACT FROM AUTHOR]

This study aims to investigate the flow characteristics of mixed convection in a parallel plate channel filled with bidisperse porous medium (BDPM). The objective is to understand the effects of momentum slip and convective boundary conditions on the channel walls. A two-velocity two-temperature model is employed to analyze the flow and temperature distributions in both the fluid and solid phases. The governing equations are made dimensionless using appropriate similarity transformations. The Homotopy Analysis Method (HAM) is utilized to solve the resulting equations and analyze the velocity and temperature profiles. The influence of thermal radiation on temperature regulation is explored by controlling its intensity. The impact of the Biot number on enhancing the Nusselt number, a measure of convective heat transfer, is identified. Additionally, the study investigates the effects of various parameters on velocity, temperature, Nusselt number and skin friction. Graphical representations of these relationships are presented, and the findings are discussed comprehensively. [ABSTRACT FROM AUTHOR]

Processing of renewable, abundant, and low-cost biomass into graphene materials such as porous carbon materials for application in the environmental field, electronics and clean energy has been attracting interest in the last few decades. In this study, activated carbons (ACs) were produced via the carbonization of rice husk carbon (ash-less without silica), followed by chemical activation with KOH at 650 °C and 750 °C for 2 h/N2 gas flow. Then, utilizing an improved Hummers' method (Tour method) with modifications, graphene oxide (GO) samples were synthesized from the rice husk-based activated carbons as an alternative to graphite. Also, applying the Tour method, followed by a catalytic hydrothermal step, reduced graphene oxide (rGO) was obtained. FESEM and TEM images exhibited the formation of graphene oxide sheets after the oxidation of AC-KOH650 °C and AC-KOH650 °C. Furthermore, Raman, FTIR and UV-vis spectra characterized the presence of defects, oxygen functional surface groups and absorption bands, indicating the enhanced properties of graphene oxide prepared from graphite flakes through the improved Hummers' method. In comparison to pure GO, the graphitized activated carbons from rice husk were successfully oxidized to GO samples and reduced to rGO after hydrothermal treatment with high yield and good quality. [ABSTRACT FROM AUTHOR]

In this study, waste tires (WTs) were carbonized under an N2 atmosphere. Subsequently, KOH/WTs‐char with KOH‐assisted CO2 activation was used to prepare activated carbon (AC) as a highly porous carbon material for the removal of Cr(VI) and Cd(II) from water. Various techniques such as elemental analysis, Fourier‐transform infrared spectroscopy, scanning electron microscopy, and N2 adsorption/desorption were employed to investigate the physical and chemical characteristics of the prepared carbons. The WTs‐char activated with KOH under CO2 exhibited a microstructure with a high BET surface area and pore volume of 1841 m2/g and 0.869 cm3/g, respectively, demonstrating excellent adsorbent performance. The maximum removal efficiencies of 99.91 % for Cd(II) and 99.81 % for Cr(VI) were achieved using AC2 carbon under the following conditions: pH 2 for Cr(VI) and pH 5 for Cd(II), contact time of 120 min, adsorbent dose of 0.4 g/100 mL, and temperature of 298 K. The adsorption kinetics followed the pseudo‐second‐order equation, and the equilibrium data fit well with the Redlich–Peterson isotherm equation. The positive values of ▵G indicated that the uptake process for both ions was nonspontaneous and nonfeasible over the temperature studied. Both ions showed negative values of ΔH and ΔS on carbon, suggesting exothermic adsorption and a decrease in disorder. Regeneration studies showed that NaOH was a better desorbing agent than HCl. Cr(VI) desorption resulted in over 90 % removal recovery by AC2 using 1.0 M NaOH even after the fifth cycle. However, the low activation energy indicated that the adsorption was favorable kinetically. Overall, this study demonstrated the effective preparation of highly porous carbon and its successful performance in removing Cr(VI) and Cd(II) ions. [ABSTRACT FROM AUTHOR]

Corn stalk and diatomite were cross-linked by N,N'-Methylenebisacrylamide (MBA) to obtain gel porous materials for methylene blue adsorption, which improved the multi-element pores effect. The process solved the difficult recovery problem of powder adsorbents as well. Results showed that the optimal preparation conditions of corn stalk/diatomite gel porous materials were: 1 mL of glutaraldehyde, 6 g of acrylic acid, 150 mg of MBA and 100 mg of potassium persulfate. The adsorption process conditions were optimized: At the pH = 8, 8 mg of gel porous material was adsorbed for 1 hour. Under the optimal conditions, the removal percentage was 93.65% and the adsorption capacity reached 288.43 mg/g. The characterization results indicated that the corn stalk was successfully combined with diatomite. Corn stalk/diatomite gel porous materials had a three-dimensional network structure with more active sites. The adsorption isotherms fit the Langmuir model. Furthermore, the adsorption kinetics fit the pseudo-second-order model. The adsorbent surface is uniform and the adsorption process is mostly monolayer adsorption. The adsorption process includes chemical and physical adsorption. The maximum saturated adsorption capacity was 657.89 mg/g. Corn stalk/diatomite gel porous materials maintained good adsorption performance after cyclic adsorption. The adsorbent prepared in this study has a good regeneration cycle and methylene blue removal capacity. [ABSTRACT FROM AUTHOR]

Assessing the feasibility of porous formations for hydrogen geo-storage demands a comprehensive understanding of hydrogen (H 2) transport behavior in porous media at subsurface conditions. In this study, we employ molecular dynamics simulations to evaluate the effects of pressure (20–500 atm), pore size (2–20 nm), and surface composition on H 2 diffusion and interactions within organic and inorganic slit pores. Our analysis of H 2 density profiles and interaction energies reveals a distinct preference for H 2 molecules to adsorb more readily onto graphene surfaces than kaolinite surfaces. However, self-diffusion results demonstrate that H 2 molecules interact relatively weakly with both substrate types. Further insights are provided by velocity autocorrelation functions, emphasizing the occurrence of wall-mediated collisions as H 2 molecules diffuse along the pore surfaces, particularly within kaolinite. This highlights the significance of surface roughness in mitigating H 2 loss via diffusion in subsurface nanopores, given the small molecular size of H 2 and its limited interactions with both organic and inorganic materials. Furthermore, the results demonstrate that self-diffusion coefficients in both pore types increase with pore size and decrease with pressure. Notably, surface composition plays a critical role in low-pressure environments, with self-diffusion coefficients beginning to converge beyond a pressure of 100 atm. Self-diffusion coefficients also become less sensitive to slit aperture beyond a pressure of 50 atm. In high-pressure environments, hydrogen transport is governed by thermal collisions between gas molecules, leading to negligible property variations between pore types. These findings hold significance in the investigation of efficient H 2 storage within porous media and caprock formations. • H 2 molecules adsorb more readily onto graphene surfaces than kaolinite surfaces. • H 2 molecules interact relatively weakly with both graphene and kaolinite. • Surface roughness is a fundamental property governing potential H 2 loss. • H 2 self-diffusion generally increases with pore size and decreases with pressure. • Surface composition plays a critical role in H 2 transport at lower pressures. [ABSTRACT FROM AUTHOR]

Taking Bingham slurry as the research object, an infiltration diffusion model of Bingham slurry in unsaturated soil is established based on the seepage theory of unsaturated porous media, which takes into account the displacement effect and the viscosity time-varying characteristics of slurry. Combined with the seepage motion equation, relevant boundary conditions and interface conditions, the Bingham slurry diffusion equation considers grouting parameters and mechanical parameters is obtained. The research results are degraded to the saturated state and compared with the existing theoretical results. Numerical examples are used to study the influence of the above parameters on grouting pressure and slurry diffusion radius, then the diffusion mechanism of Bingham slurry is verified and analysed by model test. The above analysis and test results confirm the effectiveness and applicability of the research results, which can provide reliable theoretical support and technical reference for the design and construction of grouting engineering in unsaturated soil areas. [ABSTRACT FROM AUTHOR]

A significant aspect of fluid flow in a porous medium is its properties' variation which affects velocity and pressure fields. This work evaluates fluid flow in a 3D‐printed porous medium structure filled with rocky particles. The experimental data were used to propose a pressure drop model and evaluate the accuracy of a pseudohomogeneous approximation. A porous medium with permeability of 8.95 × 10−10 m2 was used in both experiments and simulations. Parameters for the model were estimated and compared to the simulation results. The deviation between experimental and simulated pressure drop across the bed was within 6.00 % for laminar flow regimes, while for transition flow regimes more significant deviations were observed. [ABSTRACT FROM AUTHOR]