Conventional Porous Materials Research Articles

Regulating the “core-shell” microstructure of hard carbon through sodium hydroxide activation for achieving high-capacity SIBs anode

Pore structure engineering has been acknowledged as suitable approach to creating active sites and enhancing ion transport capabilities of hard carbon anodes. However, conventional porous carbon materials exhibit high BET and surface defects. Additionally, the sodium storage mechanism predominantly occurs in the slope region. This contradicts practical application requirements because the capacity of the plateau region is crucial for determining the actual capacity of batteries. In our work, we prepared a novel “core-shell” carbon framework (CNA1200). Introducing closed pores and carboxyl groups into coal-based carbon materials to enhance its sodium storage performance. The closed pore structure dominates in the “core” structure, which is attributed to the timely removal of sodium hydroxide (NaOH) to prevent further formation of active carbon structure. The presence of closed pores is beneficial for increasing sodium ion storage in the low-voltage plateau region. And the “shell” structure originates from coal tar pitch, it not only uniformly connects hard carbon particles together to improve cycling stability, but is also rich in carboxyl groups to enhance the reversible sodium storage performance in slope region. CNA1200 has excellent electrochemical performance, it exhibits a specific capacity of 335.2 mAh g−1 at a current density of 20 mA g−1 with ICE = 51.53 %. In addition, CNA1200 has outstanding cycling stability with a capacity retention of 91.8 % even when cycling over 200 times. When CNA1200 is used as anode paired with Na3V2(PO4)3 cathode, it demonstrates a capacity of 109.54 mAh g−1 at 0.1 C and capacity retention of 94.64 % at 0.5 C. This work provides valuable methods for regulating the structure of sodium-ion battery (SIBs) anode and enhances the potential for commercialization.

Solar-heated mono-domain-structured ferrimagnetic cellulosic sponge fabricated by using bidirectional freeze casting for energy-efficient liquid adsorption

Liquid adsorption has a wide range of industrial and environmental applications. In recent years, interest in liquid adsorption technology that leverages porous materials has surged, primarily driven by these materials’ substantial surface area and adjustable wettability. However, high tortuous structures of conventional porous materials impede the flow of liquids, limiting their applicability in situations requiring rapid liquid adsorption such as oil spill cleanups. This study proposed two strategies for rapid liquid adsorption. We introduced a polydimethylsiloxane (PDMS) wedge to control ice crystal growth by generating a dual temperature gradient. This led to a mono-domain lamellar structure composed of vertically aligned channels. Cubic iron oxide nanoparticles (CION) were also utilized to enhance solar heating, that enabled rapid adsorption, even of high-viscosity liquids, without an external power supply unit for heating sorbents. The application of a solar-heated ferrimagnetic cellulosic sponge with precisely controlled channels facilitates the rapid removal of high-viscosity oils, which have traditionally been challenging for large-scale oil spill cleanups in oceans.

Improvement of sound absorption of porous materials through periodic holes of sinusoidal decreasing profile

Porous materials used in several engineering applications for noise attenuation present poor acoustic performance at low frequencies. In this paper, a design of porous materials with various periodic decreasing hole profiles is presented and studied using the finite element method. The sound absorption coefficient and the normalized surface impedance are compared for different periodic decreasing hole profiles. A small drop in sound absorption is observed after the first peak with a decreasing linear profile. Using a sinusoidal decreasing hole profile, it is shown that the drop is attenuated. The impacts of the amplitude and the period of the sinusoidal profile on the sound absorption coefficient and the surface impedance are demonstrated. The proposed porous material design with periodic holes having a sinusoidal decreasing profile shows a significant improvement in sound absorption over a large frequency band compared to conventional porous materials.

Combination of a 3D-printed microperforated panel and a Helmholtz resonators array for low-frequency sound absorption

The application of solutions based on conventional porous materials for low-frequency sound absorption is often limited to the available space for their installation, as these require a significant thickness to be efficient. A system combining of a microperforated panel with an array of Helmholtz resonators, properly designed, can provide effective noise absorption at low- and mid-frequencies with a limited thickness. In this work, the sound absorption coefficient of several systems of this type was assessed by analytical calculations, numerical simulations and experiments carried out in an impedance tube according to the standard ISO 10534-1:1996. The prototypes were 3-D printed using recycled materials. The absorption coefficient, analytically obtained, was significantly higher than that measured. However, the results from numerical simulations are in good agreement with measurements, showing that the numerical model carried out can be used for further studies to optimize the system design. An example is given by increasing of the number of Helmholtz resonators in the array, that yields an increase in the sound absorption. Results show the potential of this type of solutions to be used for low-frequency noise absorption in applications where the available space is limited.

Fe‐Based Metal‐Organic Frameworks: From Various Synthesis, Diverse Structures to Multifunctional Applications

Comprehensive SummaryIron‐based metal‐organic frameworks (Fe‐MOFs) have attracted extensive interest from researchers due to their tunability, favorable properties, and chemical versatility. Compared with conventional porous materials, Fe‐MOFs exhibit better performance in a wide variety of applications. Herein, the structures of Fe‐MOFs are summarized to explore potential structures based on isoreticular chemistry, as well as the recent research progress in their synthesis and multifunctional applications. The rapid development of Fe‐MOFs has broadened the application range of Fe‐MOFs, and a brief description of Fe‐MOF applications in gas storage and separation, catalysis, bioimaging, and magnetism is outlined, with the aim to expand the prospects of Fe‐MOFs in more practical applications.

Loofah-inspired sodium alginate/carboxymethyl cellulose sodium-based porous frame for all-weather super-viscous crude oil adsorption and wastewater treatment in harsh environment

Solar-driven viscosity reduction of highly viscous crude oil has emerged as an environmentally friendly method to address large-scale oil spills. However, the challenge lies in the limited availability of sunlight during cloudy days and at night, which hinders the effectiveness of green advanced porous materials. This study developed all-weather-available advanced porous materials in the form of loofah-like structured porous frame composed of 1H, 1H, 2H, 2H-perfluorooctyltriethoxysilane/MXene/carbon nanotubes (CNTs)/sodium alginate (SA)/carboxymethyl cellulose sodium (NaCMC). MXene and CNTs formed a continuous and stable network that enabled PMCSCPs to rapidly reduce crude oil viscosity for all-day based on photothermal and electrothermal conversions. Additionally, loofah-like porous structure and oriented pipeline biomass skeleton endowed PMCSCPs with stable and rapid adsorption capacity and speed. Considering the complexity of the external environment and oily wastewater composition, we verified the separation performance of PMCSCPs for metal ions and dyes and the ice-breaking ability under icy conditions. PMCSCPs provided a novel approach to achieving clean, high-efficiency, all-day remediation of ultra-viscous crude oil. This “Three birds with one stone” approach is expected to be obtained from nature and used on a large scale, replacing conventional porous adsorbent materials.

Ultra-broadband acoustic absorption with inhomogeneous high-order Fabry–Pérot resonances

We present an ultra-broadband acoustic metamaterial with inhomogeneous high-order Fabry–Pérot (FP) resonances that achieves near-perfect continuous absorption in the range of 400–10000 Hz. The unit is composed of multiple FP channels with inhomogeneous cross-sectional areas, allowing for flexible adjustment of the impedance characteristics of each channel. This approach prevents the high-order peaks’ resistances from increasing rapidly and ensures a smooth resistance characteristic across a broad frequency range. As a result, the absorption performance in the high-frequency range above 3000 Hz can be significantly enhanced, eliminating the need for conventional porous materials. The inhomogeneous high-order absorption mechanism is investigated thoroughly by theoretical calculations and finite element simulations. By critically coupling the FP channels, a 27-cell broadband metamaterial is obtained with an average absorption coefficient above 90% over 400–10000 Hz, which is verified by experiments in a square impedance tube and an alpha-cabin reverberation room, respectively. Characterized by its extraordinary performance and easy-fabricated structure, this metamaterial has great potential in noise control engineering applications, especially in environments with low temperature, high humidity, or significant dustiness.

Materials Space‐Tectonics: Atomic‐level Compositional and Spatial Control Methodologies for Synthesis of Future Materials

AbstractReactions occurring at surfaces and interfaces necessitate the creation of well‐designed surface and interfacial structures. To achieve a combination of bulk material (i.e., framework) and void spaces, a meticulous process of “nano‐architecting” of the available space is necessary. Conventional porous materials such as mesoporous silica, zeolites, and metal–organic frameworks lack advanced cooperative functionalities owing to their largely monotonous pore geometries and limited conductivities. To overcome these limitations and develop functional structures with surface‐specific functions, the novel materials space‐tectonics methodology has been proposed for future materials synthesis. This review summarizes recent examples of materials synthesis based on designing building blocks (i.e., tectons) and their hybridization, along with practical guidelines for implementing materials syntheses and state‐of‐the‐art examples of practical applications. Lastly, the potential integration of materials space‐tectonics with emerging technologies, such as materials informatics, is discussed.

Advanced Metal–Organic Frameworks for Gas Separation

In the chemical process, the effective separation of small gaseous molecules with similar physical and chemical properties is of great significance. In addition, clean energy sources such as hydrogen and methane are regarded as an ideal alternative to conventional fossil fuels. However, at present, the storage technology of this kind of natural gas is not perfect. The entry of harmful substances produced by human activities into the atmosphere has become a global danger that is becoming more and more worrying. It has become an important topic for scholars and industries Development of a multi-stage channel structure with high efficiency and low energy consumption for effective separation, storage or capture of toxic and harmful substances. In order to solve this problem, we intend to study the adsorption and adsorption of MOFs in the environment aboutH2/N2, H2/CO and H2/CH4 and some other gases. Compared with molecular sieve, activated carbon and other conventional inorganic porous materials, MOFs have a broad application prospect in gas adsorption and storage with unique properties. At present, the research of metal-organic frame materials with high stability has made great progress. Through the implementation of this project, it is expected to promote its wide application in air pollution control and other aspects.

A porous metal-organic cage liquid for sustainable CO2 conversion reactions

Porous liquids are fluids with the permanent porosity, which can overcome the poor gas solubility limitations of conventional porous solid materials for three phase gas-liquid-solid reactions. However, preparation of porous liquids still requires the complicated and tedious use of porous hosts and bulky liquids. Herein, we develop a facile method to produce a porous metal-organic cage (MOC) liquid (Im-PL-Cage) by self-assembly of long polyethylene glycol (PEG)-imidazolium chain functional linkers, calixarene molecules and Zn ions. The Im-PL-Cage in neat liquid has permanent porosity and fluidity, endowing it with a high capacity of CO2 adsorption. Thus, the CO2 stored in an Im-PL-Cage can be efficiently converted to the value-added formylation product in the atmosphere, which far exceeds the porous MOC solid and nonporous PEG-imidazolium counterparts. This work offers a new method to prepare neat porous liquids for catalytic transformation of adsorbed gas molecules.

Efficient recovery of highly viscous crude oil spill by superhydrophobic ocean biomass-based aerogel assisted with solar energy

The crude oil spills is one of the crucial ocean environmental disaster. The low fluidity of high-viscosity crude oil poses significant challenges for its penetration into conventional porous adsorption materials. Fortunatelly, the viscosity of crude oil is especially temperature-sensitive, leading to the extensive research on porous materials that utilize solar heat for heat generation. In this work, we propose a biodegradable marine bio-based aerogel (PDMS-Ink@CS) with aligned channel structure via directional freeze casting technique, primarily composed of chitosan and cuttlefish ink. The PDMS-Ink@CS demonstrates excellent photothermal conversion and oil adsorption performance. We systematically investigated the effects of sunlight intensity and pore structure on the viscosity-reduction and adsorption rate of crude oil. Under simulated sunlight intensity of 1 kW m−2, the surface temperature of PDMS-Ink@CS aerogel reaches approximately 70 ℃ within 60 s, allowing to absorb crude oil 18 times its weight and recover via extrusion. When combined with a vacuum pump device, the PDMS-Ink@CS aerogel realizes the continuous recovery of crude oil from the seawater surface. Moreover, the separation efficiency of PDMS-Ink@CS aerogel for W/O emulsions can reach 99 %, which greatly broadens its range of applications. Particularly noteworthy is the fact that the PDMS-Ink@CS aerogel biodegrades within 30 days without causing environmental pollution. Thus, this super-hydrophobic ocean biomass-based chitosan aerogel exhibits vast potential for oil spill recovery applications.

Ratio-Tuning of Silica Aerogel Co-Hydrolyzed Precursors Enables Broadband, Angle-Independent, Deformation-Tolerant, Achieving 99.7% Reflectivity.

The super-white body might be defined as its reflectivity exceeding 98% at any angle in the visible light spectrum, which can be used in a variety of emerging fields including optics, energy, environment, aerospace, etc. However, elaborate synthesis of a light-weight, highly reflective super-white aerogel body remains a great challenge. In this work, fine-tuning of silica aerogel co-hydrolyzed precursor ratios, 99.7% reflectivity with angle-independence in the visible light spectrum has been successfully achieved when the areal density is only 0.129g cm-2 , which breaks through the theoretical bandwidth limit of photonic crystals as well as the measured reflectivity limit of conventional porous materials. Furthermore, the reflectivity of super-white silica aerogel remains unchanged after various harsh deformations including compression and bending 1000 times, solar (≈800W m-2 ), ultraviolet (≈0.68W m-2 ), and humidity (100%) aging for 100 days, liquid nitrogen (-196°C) and high-temperature (300°C) thermal shock 100 times. As proofs of performance, the resulting super-white silica aerogels have been used as the novel standard white plate for better spectrum calibration, as the flexible projector curtains for optical display, as well as the transmitted light reflective layer in the photovoltaic cell for improving the relative power conversion efficiency of 5.6%.

Numerical Prediction and Correlations of Effective Thermal Conductivity in a Drilled-Hollow-Sphere Architected Foam

Abstract Additive manufacturing is now a promising option to obtain porous customized structures at relatively low scales. The capability to design structures with tunable heat transfer performance compared to conventional porous materials, such as open-cell foams, is very interesting to the user. In this study, we investigated heat conduction in a drilled-hollow-sphere architected foam, inspired by Triply-Periodic Minimal Surfaces (TPMS) and foam structures, generated using perforated spherical hollow shells connected with cylindrical binders. Temperature fields and heat fluxes in the foam were predicted numerically, and the effective thermal conductivity of the foam was calculated for different sets of the binder angle, the shell thickness, and the perforation radius. The dependence of the foam porosity on the binder angle and perforation radius was also pointed out. Predictions were validated by comparing them with data available from the literature. Results showed that varying the characteristics of the investigated drilled-hollow-sphere architected foam, its predicted effective thermal conductivity can be adjusted by more than one order of magnitude larger or smaller than that of conventional foams, making architected foams promising enhancers of their heat transfer performance. Finally, new dimensionless correlations among the effective thermal conductivity and some significant morphological parameters of the foam were derived and presented for practical use.

Equivalent Circuit Method Based Double Layer Micro-perforated Panel (MPP) Design to Widen the Sound Absorption Bandwidth

Acoustical solutions that occupy minimum space and simultaneously allow for flexibility in interior spaces are not feasible by using thick absorbers like conventional porous and fibrous materials. Micro-perforated panels are an excellent alternative to those classical materials due to their environmental friendliness, design flexibility on various materials, and easy installation. However, they come with the handicap of having a very narrow absorption frequency bandwidth. This study explores two inhomogeneous microperforated layers arranged in a cascade with different back cavities in order to widen the sound absorption bandwidth. This serial-parallel architected MPP system is investigated by mathematical models using Maa's model for a single MPP and the Equivalent Circuit Method (ECM). The numerical results were validated through experiments for normal sound incidence in the impedance tube using the transfer function method. Increasing the back cavity length of the MPP having a higher perforation ratio and larger holes results in a higher absorption in the high-frequency range. In contrast, combinations of larger cavity lengths and smaller perforation ratios are more effective in the low-frequency spectrum. By tuning the design parameters of those structures, it is possible to achieve wideband absorption by fibreless materials for room acoustic applications.

Constructing Mechanical Shuttles in a Three-dimensional (3D)Porous Architecture for Selective Transportof Lithium Ions.

Lithium(Li)extraction from brinesis a major barrier to the sustainable development of batteries and alloys;however, current separation technology suffers from a trade-off between ion selectivity andpermeability. Herein, a crown ether mechanically interlocked 3D porous organic framework (Crown-POF) was prepared as the porous filler of thin-film nanocomposite membranes. Crown-POF with penta-coordinated(four O crown atoms and one N tert-amine atom)adsorptionsites enables a special recognition for Li+ion. Moreover, thefour N tert-amine atoms on each POF branch facilitate the flipping motion of Li+ion along the skeletal thread, while retaining the specified binding pattern. Accordingly, the crown ether interlocked POF network displays an ultrafast ion transfer rate, over 10 times that of the conventional porous materials.Notably, the nanocomposite membrane gives high speed and selectivity for Li+ion transport as compared with other porous solid-based mixed-matrix membranes.

Constructing Mechanical Shuttles in a Three‐dimensional (3D) Porous Architecture for Selective Transport of Lithium Ions

AbstractLithium (Li) extraction from brines is a major barrier to the sustainable development of batteries and alloys; however, current separation technology suffers from a trade‐off between ion selectivity and permeability. Herein, a crown ether mechanically interlocked 3D porous organic framework (Crown‐POF) was prepared as the porous filler of thin‐film nanocomposite membranes. Crown‐POF with penta‐coordinated (four Ocrown atoms and one Ntert‐amine atom) adsorption sites enables a special recognition for Li+ ion. Moreover, the four Ntert‐amine atoms on each POF branch facilitate the flipping motion of Li+ ion along the skeletal thread, while retaining the specified binding pattern. Accordingly, the crown ether interlocked POF network displays an ultrafast ion transfer rate, over 10 times that of the conventional porous materials. Notably, the nanocomposite membrane gives high speed and selectivity for Li+ ion transport as compared with other porous solid‐based mixed‐matrix membranes.

Room temperature synthesis of monolithic MIL-100(Fe) in aqueous solution for energy-efficient removal and recovery of aromatic volatile organic compounds.

The removal and recovery of volatile organic compounds (VOCs) are widely used in many industrials. Unfortunately, most conventional porous materials not only have low VOCs uptake, but also need to be regenerated at relatively high temperature. Metal-organic frameworks (MOFs) have great potential for the removal and recovery of VOCs as their record-breaking gas adsorption capacity, easy regeneration, tunable pore structure and functional groups. Whereas, powdered MOFs are hardly implemented in industrial fields owing to their low bulk density and high pressure drop. Exploring a green method to prepare granular MOFs for the removal and recovery of VOCs is still a challenge. Herein, we report the room temperature green synthesis of a stable Fe-based MOF monolith by using water as the solvent without applying high pressure and chemical binders. The static and dynamic experiments show that the optimized centimeter-scale monolith has high porosity and mechanical strength, and exhibits much better adsorption performance for representative aromatic VOCs (benzene, toluene and p-xylene), than commercial activated carbon and activated carbon fiber under the same conditions. Remarkably, as-synthesized monolith can be rapidly regenerated at lower temperature. These results clearly demonstrate the advantages of MOF monoliths in removing and recovering VOCs, and also provide new insight into the effects of drying temperature, washing and centrifugation procedures on MOF shaping.

Zeolite encapsulated organometallic complexes as model catalysts.

Heterogeneities in the structure of active centers in metal-containing porous materials are unavoidable and complicate the description of chemical events occurring along reaction coordinates at the atomic level. Metal containing zeolites include sites of varied local coordination and secondary confining environments, requiring careful titration protocols to quantify the predominant active sites. Hybrid organometallic-zeolite catalysts are useful well-defined platform materials for spectroscopic, kinetic, and computational studies of heterogeneous catalysis that avoid the complications of conventional metal-containing porous materials. Such materials have been synthesized and studied previously, but catalytic applications were mostly limited to liquid-phase oxidation and electrochemical reactions. The hydrothermal stability, time-on-stream stability, and utility of these materials in gas-phase oxidation reactions are under-studied. The potential applications for single-site heterogeneous catalysts in fundamental research are abundant and motivate future synthetic, spectroscopic, kinetic, and computational studies.

Introducing Polar Groups in Porous Aromatic Framework for Achieving High Capacity of Organic Molecules and Enhanced Self-Cleaning Applications.

Due to the frequent oil/organic solvent leakage, efficient oil/water separation has attracted extensive concern. However, conventional porous materials possess nonpolar building units, which reveal relatively weak affinity for polar organic molecules. Here, two different polarities of superhydrophobic porous aromatic frameworks (PAFs) were synthesized with respective orthoposition and paraposition C=O groups in the PAF linkers. The conjugated structure formed by a large number of alkynyl and benzene ring structures enabled porous and superhydrophobic quality of PAFs. After the successful preparation of the PAF solids, PAF powders were coated on polyester fabrics by a simple dip-coating method, which endowed the resulting polyester fabrics with superhydrophobicity, porosity, and excellent stability. Based on the unique structure, the oil/water separation efficiency of two superhydrophobic flexible fabrics was more than 90% for various organic solvents. Polar LNU-26 PAF showed better separation performance for the polar oils. This work takes the lead in adopting the polar groups as building units for the preparation of porous networks, which has great guiding significance for the construction of advanced oil/water separation materials.

Guest-molecule-induced self-adaptive pore engineering facilitates purification of ethylene from ternary mixture

•A variable MOF material with privileged adsorption sites is discovered •One-step purification of ethylene from a C2 ternary mixture is realized •The adsorption sites of gas molecules are precisely determined by single-crystal XRD •The purification productivity of ethylene is as high as 2.01 mmol/g Purification of ethylene from multicomponent mixtures is progressing toward one-step separation by a single material at room temperature and atmospheric pressure. However, conventional rigid porous materials cannot efficiently separate ethylene with a size close to acetylene and ethane through pore sieving. Herein, we report a cobalt metal-organic framework, UPC-66, that exhibits a self-adaptive pore structure under an external stimulus. In situ powder X-ray diffraction confirmed that the pore size of activated UPC-66-a can undergo synchronous dynamic transformation with temperature, pressure, and guest molecules. Dynamic breakthrough experiments show that the polymer-grade C2H4 can be obtained from a C2H2/C2H4/C2H6 (1/1/1 and 1/98/1) ternary mixture. The corresponding productivity of C2H4 can reach 2.01 mmol/g. The specific separation performance is attributed to the privileged adsorption sites of the self-adaptive pores, determined by the single-crystal data after gas encapsulation. This work provides valuable guidance for the application of self-adaptive pore structures in multicomponent separations. Purification of ethylene from multicomponent mixtures is progressing toward one-step separation by a single material at room temperature and atmospheric pressure. However, conventional rigid porous materials cannot efficiently separate ethylene with a size close to acetylene and ethane through pore sieving. Herein, we report a cobalt metal-organic framework, UPC-66, that exhibits a self-adaptive pore structure under an external stimulus. In situ powder X-ray diffraction confirmed that the pore size of activated UPC-66-a can undergo synchronous dynamic transformation with temperature, pressure, and guest molecules. Dynamic breakthrough experiments show that the polymer-grade C2H4 can be obtained from a C2H2/C2H4/C2H6 (1/1/1 and 1/98/1) ternary mixture. The corresponding productivity of C2H4 can reach 2.01 mmol/g. The specific separation performance is attributed to the privileged adsorption sites of the self-adaptive pores, determined by the single-crystal data after gas encapsulation. This work provides valuable guidance for the application of self-adaptive pore structures in multicomponent separations.