Rectangular Pores Research Articles

Soft and diffusion-controlled Sr-MOF for efficient separation of H2O/D2O

Heavy water (D2O) electrolysis is the primary technology for D2 production, playing an irreplaceable role in fields such as nuclear fusion research and isotope tracing. However, the inherent similarity in chemical properties between H2O and D2O (with only a 1.4 °C difference in boiling points) poses significant challenges to their separation. Furthermore, the extremely low natural abundance of D2O (0.015 %) increases the difficulty and cost of separation, while traditional electrolysis and distillation techniques are highly energy intensive. Therefore, there is an urgent need to develop novel adsorbents for efficient and environmentally sustainable H2O/D2O separation. Herein, we used polydentate ligand 2, 5-dihydroxyterephthalic acid (DOBDC) and its derivatives 4,4́-(anthracene-9,10-diyl) bis (2-hydroxybenzoic acid (ABHB) as raw materials to prepare two novel high coordination Sr-MOFs namely IPE-1 and IPE-2, respectively. These MOFs were applied for efficient separation of H2O and D2O at room temperature. X-ray diffraction results reveal that one Sr atom in IPE-1 is coordinated with 9 oxygen atoms. This high coordination number results in the formation of ultra-small rectangular pores of approximately 2.5 Å. Adsorption isotherms of N2, CO2, H2O, and D2O indicate that the ultramicroporous structure of IPE-1 precludes efficient diffusion of CO2 and H2O molecules into the MOF channels. In contrast, the activated IPE-2 exhibits good CO2, H2O, and D2O uptake capacities of 3 mmol/g, 8.38 mmol/g, and 6.51 mmol/g at 298 K, respectively. The Qst values and Ksap values of H2O and D2O indicate that the adsorption rates of H2O were much higher than D2O under 0.2 < P/P0 < 0.7, with a calculated ratio of approximately 1.26. This study not only provides appealing MOFs materials for efficient H2O/D2O separation at room temperature but also provides a new avenue for preparing adsorbents with high stability and high separation performance.

Hydrodynamic Porosity: A New Perspective on Flow through Porous Media, Part I

Pore-scale flow velocity is an essential parameter in determining transport through porous media, but it is often miscalculated. Researchers use a static porosity value to relate volumetric or superficial velocities to pore-scale flow velocities. We know this modeling assumption to be an oversimplification. The variable fraction of porosity conducive to flow, what we define as hydrodynamic porosity, θmobile, exhibits a quantifiable dependence on the Reynolds number (i.e., pore-scale flow velocity) in the Laminar flow regime. This fact remains largely unacknowledged in the literature. In this work, we quantify the dependence of θmobile on the Reynolds number via numerical flow simulation at the pore scale for rectangular pores of various aspect ratios, i.e., for highly idealized dead-end pore spaces. We demonstrate that, for the chosen cavity geometries, θmobile decreases by as much as 42% over the Laminar flow regime. Moreover, θmobile exhibits an exponential dependence on the Reynolds number, Re = R. The fit quality is effectively perfect, with a coefficient of determination (R2) of approximately 1 for each set of simulation data. Finally, we show that this exponential dependence can be easily fitted for pore-scale flow velocity through use of only a few Picard iterations, even with an initial guess that is 10 orders of magnitude off. Not only is this relationship a more accurate definition of pore-scale flow velocity, but it is also a necessary modeling improvement that can be easily implemented. In the companion paper (Part 2), we build upon the findings reported here and demonstrate their applicability to media with other pore geometries: rectangular and non-rectangular cavities (circular and triangular).

Simulation and Experimental Investigation of the Effect of Pore Shape on Heat Transfer Behavior of Phase Change Materials in Porous Metal Structures.

With the gradual increase in energy demand in global industrialization, the energy crisis has become an urgent problem. Due to high heat storage density, small volume change, and nearly constant transition temperature, phase change materials (PCMs) provide a promising method to store thermal energy. In this work, we designed and fabricated three kinds of porous metal structures with hexagonal, rectangular, and circular pores and explored the phase change process of PCMs within them. A two-dimensional numerical model was established to investigate the heat transfer process of PCMs within different shapes of porous metal structures and analyze the influence of heat source location on the thermal performance of the thermal storage units. Visualization experiments were also carried out to reveal the melting process of PCMs within different porous metal structures by a digital camera. The results show that paraffin in a porous metal structure with hexagonal pores has the fastest melting rate, while that in a porous metal structure with circular pores has the slowest melting rate. Under the bottom heating mode, the melting time of the paraffin in porous metal structures with hexagonal pores is shortened by 18.6% compared to that in porous metal structures with circular pores. Under the left heating mode, the corresponding melting time is shortened by 16.7%. These findings in this work will offer an effective method to design and optimize the structure of porous metal and improve the thermal properties of PCMs.

Molecular dynamics study of tribological properties of Ni–Cr alloy coatings with different pore shapes

The presence of nanopores with different shapes cannot be avoided during the coating preparation process, and the pore shape is an important factor affecting the coating friction mechanism. This paper applies molecular dynamics to study the tribological properties of Ni–Cr alloy coatings containing spherical, rectangular and ellipsoid-shaped pores. It is found that the coating with spherical pores has the smallest fluctuation of friction coefficient and the shallowest depth of wear scar. The atoms near the rectangular pores are more likely to move towards the corners of the pores due to shear strain, and the stress concentration in the spherical pores is less than that in the rectangular and ellipsoidal pores. The spherical pore has the least effect on the potential energy inside the coating, and the interatomic bond strength is optimal. The ellipsoidal pore is also more effective in insulating the heat transfer to the bottom of the coating, protecting the substrate underneath the coating and prolonging the coating life. Coatings with rectangular pores generate more interstitial atoms during friction, producing Frank dislocation loop and prismatic dislocation loops.

Turbulent flows over porous lattices: alteration of near-wall turbulence and pore-flow amplitude modulation

Turbulent flows over porous lattices consisting of rectangular cuboid pores are investigated using scale-resolving direct numerical simulations. Beyond a certain threshold which is primarily determined by the wall-normal Darcy permeability, ${{\mathsf{K}}_y}$ , near-wall turbulence transitions from its canonical regime, marked by the presence of streak-like structures, to another marked by the presence of Kelvin–Helmholtz-like (K–H-like) spanwise-coherent structures. The threshold agrees well with that previously established in studies where permeable-wall boundary conditions had been used as surrogates for a porous substrate (Gómez-de Segura &amp; García-Mayoral, J. Fluid Mech., vol. 875, 2019, pp. 124–172). In the smooth-wall-like regime, none of the investigated substrates demonstrate any reduction in drag relative to a smooth-wall flow. At the permeable surface, a notable component of the flow is that which adheres to the pore geometry and undergoes modulation by the turbulent scales of motions due to the interaction mechanism described by Abderrahaman-Elena et al. (J. Fluid Mech., vol. 865, 2019, pp. 1042–1071). Its resulting effect can be quantified in terms of an amplitude modulation (AM) using the approach of Mathis et al. (J. Fluid Mech., vol. 628, 2009, pp. 311–337). This pore-coherent flow component persists throughout the porous substrate, highlighting the importance of a given substrate's microstructure in the presence of an overlying turbulent flow. This geometry-related aspect of the flow is not accounted for when continuum-based models for a porous medium or effective representations of them, such as wall boundary conditions, are used. The intensity of the AM effect is enhanced in the K–H-like regime and becomes strengthened with larger permeability. As a result, structured porous materials may be designed to exploit or mitigate these flow features depending upon the intended application.

Dynamic Entwined Topology in Helical Covalent Polymers Dictated by Competing Supramolecular Interactions

AbstractNaturally occurring polymeric structures often consist of 1D polymer chains intricately folded and entwined through non‐covalent bonds, adopting precise topologies crucial for their functionality. The exploration of crystalline 1D polymers through dynamic covalent chemistry (DCvC) and supramolecular interactions represents a novel approach for developing crystalline polymers. This study shows that sub‐angstrom differences in the counter‐ion size can lead to various helical covalent polymer (HCP) topologies, including a novel metal‐coordination HCP (m‐HCP) motif. Single‐crystal X‐ray diffraction (SCXRD) analysis of HCP−Na revealed that double helical pairs are formed by sodium ions coordinating to spiroborate linkages to form rectangular pores. The double helices are interpenetrated by the unreacted diols coordinating sodium ions. The reticulation of the m‐HCP structure was demonstrated by the successful synthesis of HCP−K. Finally, ion‐exchange studies were conducted to show the interconversion between HCP structures. This research illustrates how seemingly simple modifications, such as changes in counter‐ion size, can significantly influence the polymer topology and determine which supramolecular interactions dominate the crystal lattice.

Dynamic Entwined Topology in Helical Covalent Polymers Dictated by Competing Supramolecular Interactions.

Naturally occurring polymeric structures often consist of 1D polymer chains intricately folded and entwined through non-covalent bonds, adopting precise topologies crucial for their functionality. The exploration of crystalline 1D polymers through dynamic covalent chemistry (DCvC) and supramolecular interactions represents a novel approach for developing crystalline polymers. This study shows that sub-angstrom differences in the counter-ion size can lead to various helical covalent polymer (HCP) topologies, including a novel metal-coordination HCP (m-HCP) motif. Single-crystal X-ray diffraction (SCXRD) analysis of HCP-Na revealed that double helical pairs are formed by sodium ions coordinating to spiroborate linkages to form rectangular pores. The double helices are interpenetrated by the unreacted diols coordinating sodium ions. The reticulation of the m-HCP structure was demonstrated by the successful synthesis of HCP-K. Finally, ion-exchange studies were conducted to show the interconversion between HCP structures. This research illustrates how seemingly simple modifications, such as changes in counter-ion size, can significantly influence the polymer topology and determine which supramolecular interactions dominate the crystal lattice.

Unraveling residual trapping for geologic hydrogen storage and production using pore-scale modeling

Residual trapping is an important process that affects the efficiency of cyclic storage and withdrawal and in-situ production of hydrogen in geological media. In this study, we have conducted pore-scale modeling to investigate the effects of pore geometry and injection rate on the occurrence and efficiency of residual trapping via dead-end bypassing. We begin our theoretical and numerical analyses using a single rectangular pore to understand the key controls in bypassing. We further investigated two factors affecting bypassing: (a) a continuous cycle of injection-extraction of H2, and (b) variable pore geometry. Based on our pore-scale simulations, we found that: (a) a higher pore height/width ratio (h/w) and a higher injection rate cause more residual trapping, which is unfavorable for withdrawal of H2; (b) the trapping percentage increases with the h/w first and then decreases after h/w reaches 0.5; (c) and a converging-shaped pore can result in less trapping volume. Based on a theoretical comparison of the residual trapping behavior of H2 and CO2, we discuss the mechanisms that are applicable to CO2 residual trapping and the possibility of developing engineering controls of H2 storage and production.

3D multifunctional porous pine carbon aerogels coupled with highly dispersed CoFe nanoparticles for robust electromagnetic wave response

Functional carbonaceous materials with controllable morphology, low apparent density, large surface area, and high porosity starting from natural precursors using environmentally friendly processes are an appealing topic in the electromagnetic wave (EMW) field. In this work, renewable pine woods with ordered pore channels are selected to load highly dispersed CoFe alloy nanoparticles formed by in-situ pyrolysis reaction between Fe3O4 nanospheres and ZIF-67 nanoparticles. The constructed three-dimensional (3D) porous CWA-CoFe-NC aerogel inherits the characteristics of highly dispersed small CoFe alloy nanoparticles, porous carbon aerogel with rectangular honeycomb-like structure, and abundant N heteroatoms. Therefore, CWA-CoFe-NC aerogel achieves an excellent EMW absorption performance with reflection loss (RL) values of −61.6 and −58.2 dB at matching thicknesses of 3.7 and 1.2 mm, respectively. Benefiting from the reasonable design of the composite structure and composition, 3D porous aerogel also enables great potential for multifunctional applications. Particularly, good lightweight and mechanical properties are realized in the CWA-CoFe-NC aerogels due to their ordered pore channels and abundant rectangular pores. Furthermore, good flame retardant performance can ensure the serviceability of the target device in high/low-temperature environments. In addition, CWA-CoFe-NC aerogels show good thermal stability and thermal management characteristics. This work provides a novel and effective method for the preparation of lightweight, high-performance, and multifunctional EMW absorbers.

Theoretical estimation of sound absorption characteristics in a collection of rectangular holes: Comparison with experimental results

This study quantifies the sound absorption properties of small rectangular or square pores that are less than a few millimeters per side, based solely on their geometric dimensions. Analytical solutions for the sound absorption coefficient of narrow tubes with rectangular holes have not been obtained. Therefore, alternative methods of predicting the sound absorption coefficient, such as using the circular tube approximation or the two-plane approximation, are possible. In this study, the sound absorption coefficient was estimated by several theoretical models that are considered useful for estimating the sound absorption coefficient in rectangular tubes. The results were then compared with experimental values. For square holes, the accuracy of the sound absorption coefficient increased in the order of the model considering two-sided circumference only, the circular tube model, and Allard's method based on Stinson's. In rectangular holes, Allard's method based on Stinson's showed good agreement with the experimental data across a wide range of aspect ratios. For rectangular holes, the accuracy of Stinson's two-plane approximation was superior to that of the circular tube approximation when the aspect ratio was 4. Furthermore, when the aspect ratio was 8, the accuracy of Stinson's two-plane approximation became comparable to that of Allard's method based on Stinson's.

Poly(L-co-D,L-lactic acid-co-trimethylene carbonate) for extrusion-based 3D printing: Comprehensive characterization and cytocompatibility assessment

Extrusion-based 3D printing is a well-established material processing technique that has shown promise in employing a variety of polymers. Poly(lactic acid) is the most studied and widely used raw material in 3D printing, which can be modified by copolymerization with trimethylene carbonate (TMC), for tissue engineering applications. In this study, the aim was to explore the characterization of Poly(L-co-D,L-lactic acid-co-trimethylene carbonate) (PLDLA-TMC) at different ratios (60/40, 70/30, 80/20, and 90/10), focusing on their physicochemical, thermal, and rheological characterization, as well as their cytocompatibility. The results demonstrated shear-thinning behavior and highlighted the influence of TMC content on viscoelastic properties. The printing speed of 4 mm s−1 allowed the obtaining of scaffolds with rectangular pores and controlling of extrusion temperature promoted the formation of uniform filaments with high print quality. Additionally, the cytocompatibility assessment of the scaffolds revealed the terpolymer's potential for tissue engineering across a wide range of applications.

Controlling C–C coupling reactivity through pore shape engineering of B-doped graphyne family

Graphyne is an interesting carbon allotrope characterized by sp-sp2 hybridized carbon bonds, which allow for structure variability. Though there are studies evaluating the electrical and mechanical properties of various structures, studies utilizing its structural variety toward catalyst applications are minor. In electrocatalytic CO2 reduction reactions (CRR), producing valuable C2+ products, such as C2H4 or C2H5OH, under mild conditions is still challenging. The bottleneck has been assigned to the carbon-carbon (C–C) coupling reaction, such as 2*CO → *OCCO. In this reaction, one requires strong binding to the catalyst to enhance neighboring CO concentration, but at the same time, one needs to have low C–C coupling barriers making the OC-CO bond. Following our previous study, which showed B-doped γ-graphyne can be a catalyst for ethanol production, we conducted theoretical investigations on a range of B-doped graphyne families using density functional theory. Out of the 15 different structures studied, four, 4,12,2-, sR-, γ-, and 6,6,12-graphynes, show promising potential for CRR. B-doped 4,12,2-graphyne, with small square and rectangular pores, had a very low C–C coupling barrier of 0.34 eV with strong 2*CO adsorption (−2.5 eV). Furthermore, our research revealed a correlation between the heat of reaction (2*CO → *OCCO) and the average pore area around the acetylenic linker reaction site. Smaller pores give a favorable orientation of two CO molecules, resulting in low reaction barriers.

Effect of Porosity and Pore Shape on the Mechanical and Biological Properties of Additively Manufactured Bone Scaffolds.

This study investigates the effect of porosity and pore shape on the biological and mechanical behavior of additively manufactured scaffolds for bone tissue engineering (BTE). Polylactic acid scaffolds with varying porosity levels (15-78%) and pore shapes, including regular (rectangular pores), gyroid, and diamond (triply periodic minimal surfaces) structures, are fabricated by fused filament fabrication. Murine-derived macrophages and human bone marrow-derived mesenchymal stromal cells (hBMSCs) are seeded onto the scaffolds. The compressive behavior and surface morphology of the scaffolds are characterized. The results show that scaffolds with 15%, 30%, and 45% porosity display the highest rate of macrophage and hBMSC growth. Gyroid and diamond scaffolds exhibit a higher rate of macrophage proliferation, while diamond scaffolds exhibit a higher rate of hBMSC proliferation. Additionally, gyroid and diamond scaffolds exhibit better compressive behavior compared to regular scaffolds. Of particular note, diamond scaffolds have the highest compressive modulus and strength. Surface morphology characterization indicates that the surface roughness of diamond and gyroid scaffolds is greater than that of regular scaffolds at the same porosity level, which is beneficial for cell attachment and proliferation. This study provides valuable insights into porosity and pore shape selection for additively manufactured scaffolds in BTE.

Van der Waals interaction energies for ferric ion sensors using prismatic and cylindrical pore approximations for a MOF pore.

Using the Lennard-Jones potential, we determine analytical expressions for van der Waals interaction energies between a point and a rectangular prism-shaped pore, writing them in terms of standard elementary functions. The parameter values for a new ferric ion sensor are used to compare these calculations with the cylindrical pore approximation for the interactions between an ion and a metal organic framework (MOF) pore. The results using the prismatic pore approximation predict the same qualitative outcomes as a cylindrical pore approximation. However, the prismatic approximation predicts lower magnitudes for both the interaction potential energy minimum and the force maximum, since the average distance from the centre-line to the surface of the prism is greater. We suggest that in some circumstances it is sufficient to use the simpler cylindrical approximation, provided that the cylinder radius is chosen so that the cross-sectional area is equal to the area of the prism pore opening. However, atoms at the nodes should remain approximated by semi-infinite lines. We also determine the interaction between a second ferric ion and a blocked MOF pore; as expected, the second ferric ion experiences a force away from the pore, implying that approaching ferric ions can only occupy vacant MOF pores.

Sexual dimorphism and bilateral difference of fingerprint sweat pore among Slovak population

Third level dermatoglyphic markers show a high level of individuality. Despite this fact, the occurrence of individual sweat pore types is still insufficiently studied due to their problematic extraction. The aim of our study was to evaluate the variability of sweat pore types on distal fingertips in the Slovak population and to establish the most uniform method for delineating the evaluated fingerprint area of 1 cm2 in size to avoid bias in the obtained data. In this study, the variability of seven sweat pore types (round, rhomboid, elliptical, square, rectangular, triangular, hexagonal) on distal phalanges were investigated in a sample of 60 volunteers (30 females and 30 males) from the Slovak population. The evaluated area was 1 cm2. Since none of the previously used definition methods seems to be completely reliable, we developed our own method using individual types of dermatoglyphic patterns. This method allowed an uniform location of the studied fingerprint area. The results suggest that sweat pores, like other dermatoglyphic characteristics, have strong identification potential. Several statistically significant bilateral and intersexual differences were found in both male and female populations. Significant intersexual differences in all categories were found in rhomboid and rectangular sweat pore types. Their use could be applied to partial or otherwise unusable fingerprints. The results of this study could help to incorporate these prints into the identification process, allowing their full use.

Numerical simulation of bubble rising in porous media using lattice Boltzmann method

Rising bubble systems in porous media exist in a variety of industrial processes. However, the flow characteristics of the issue are not well understood. In this work, the rising of bubble/bubbles through two types of porous structures, namely, in-line structured pore and staggered structured pore, are studied using a large density ratio lattice Boltzmann model. The effects of Eötvös number, pore shape, viscosity ratio, initial bubble number, and arrangement manner of the initial bubbles on the bubble deformation, bubble rising velocity, residual bubble mass, bubble perimeter, and the number of bubble breakups are investigated. It is found that as the Eötvös number increases, the bubbles are more easily broken during the process of passing through the porous media, the shapes of the sub-bubbles deviate from the original ones more and more, the bubble perimeter increases, and the difference between the bubble dynamics obtained by the in-line and staggered porous media decreases. Compared to the results of circular and rectangular pores, the bubble rising through the diamondoid pore has a more considerable deformation, which causes a slower rising speed. Furthermore, in the case that two bubbles are originally placed under the porous medium, the bubble deformation is greater and the bubble fracture times increase if the initial bubbles are aligned vertically. The findings of this work can contribute to the understanding of gas–liquid two-phase flow in porous media.

Robust Nickel Aspartate Framework for Shape Recognition of Hexane Isomers

Adsorption separation of linear and branched alkane isomers provides an energy-saving alternative way to improve the octane number of gasoline compared to distillation, while zeolite 5A is nearly the only commercialized adsorbent for this process. Although metal–organic frameworks are widely considered to be more promising than traditional zeolites owing to their designability and tunability, the industrial application is hindered by their low stability, high cost, or other issues. Herein, using readily available biobased l-aspartic acid as a ligand, a sustainable and low-cost microporous material, termed as Ni-Asp, is constructed and proved to be effective for recognition and adsorption separation of n-hexane from its branched isomers. The appropriate rectangular pore with uniformly distributed O-sites from monodentate carboxyl groups along the channel endows Ni-Asp with strong affinity toward n-hexane, while excluding branched isomers, which is discussed in detail by DFT calculations and verified by column breakthrough experiments. In addition, intraframework hydrogen bonds between the ammino and carboxyl groups of L-Asp further stabilize the coordination network, making Ni-Asp an ultrastable MOF. Considering the environment-friendly aqueous growing conditions, Ni-Asp shows a great potential in the adsorption application for hexane isomer separation.

A geometrical criterion for the dynamic snap-off event of a non-wetting droplet in a rectangular pore–throat microchannel

In porous media, non-wetting phase droplets snapping off in a constricted microchannel are one of the most common phenomena in two-phase flow processes. In this paper, the application range of the classic quasi-static criterion in rectangular cross section microchannels is obtained. For three different droplet breakup phenomena—total breakup, partial breakup, and non-breakup—observed in experiments when a non-wetting phase droplet passes through a microchannel constriction, the breakup is caused by the droplet neck snapping off in a channel constriction. A critical criterion for the dynamic snap-off event in a two-phase flow is proposed considering the effect of viscous dissipation by mechanical analysis, energy dissipation analysis, and many microfluidic experiments. When the droplet front flows out of the constriction, snap-off will occur if the surface energy release exceeds the required energy for viscous dissipation and kinetic energy conversion. The unique partial breakup phenomenon is affected by droplet surfactant distribution and the acceleration effect in the constriction center. This partial breakup phenomenon in experiments is an essential evidence for the non-uniform distribution of surfactants in the droplet surface. The results of this study contribute to understanding pore-scale mass transfer and flow pattern changes within porous media.

Control one-dimensional length of rectangular pore on graphene membrane for better desalination performance

At present, there is a general contradiction between permeability and selectivity of reverse osmosis (RO) membranes for desalination; a membrane with higher water permeability will give a lower salt rejection or selectivity, and vice versa. In this work, single-layer nanoporous graphene is used as RO membrane to investigate the effects of pore shape to reduce this contradiction by molecular dynamics simulations. Two kinds of pores (round and rectangular pores) with different sizes are simulated. For round pore, although the water permeability increases with the increase of the pore size, the salt rejection rate drops rapidly. For rectangular pore, reasonable designed pore structure can achieve improved water permeability and high salt rejection of graphene membrane by keeping one-dimensional length (i.e. the width) of the pore less than the size of the hydrated ions and increasing the other dimensional length. The restriction of one dimension can prevent the passage of hydrated ions through the pore effectively. This ‘one-dimensional restriction’ provides a simple strategy for designing RO membrane with variable pore structures to obtain a better desalination performance.

Crystal structures of the solvate and two tetralkylammonium inclusion compounds of [1, 2, 4, 5-tetra(4'-carboxyphenyl) - benzene

This article reports [1, 2, 4, 5-tetra(4'-carboxyphenyl)-benzene] (1) and its tetraethyl ammonium and tetrabutylammonium inclusion compounds (C34H21O8 −·N+(C2H5)4·H2O (2) C34H21O8 −·N+(n-C3H7)4·H2O (3). Compound one eventually forms a "molecular column" along the direction of [110], and the solvent molecules are filled by two adjacent columns to form a stable crystal structure. In compound 2, the tetravalent host anion forms rectangular three-dimensional pores with water molecules by O-H… O hydrogen bonds, two tetraethyl ammonium ions are neatly arranged in the pores to form a tighter structure, In structure 3, the formation of the main skeleton mainly relies on O…H…O hydrogen bond formed by the contact between the proton H shared between the two host anions and the O-H…O generated by the water molecule and one of the two anions. In the three crystal structures, [1, 2, 4, 5-tetra(4'-carboxyphenyl)-benzene], as an “X” polycyclic polycarboxylate aromatic molecule, constructs a large 3 D hole by using its configuration feature. Corresponding solvent molecules and different guest molecules are contained in the 3 D pores, forming various stable crystal structures.