Hierarchical Porous Materials Research Articles

Mesoporous N-doped hierarchical porous materials derived from core-shell MOFs: A promising strategy for eliminating sulfamethoxazole using 1O2

Slfamethoxazole (SMX) has been considered as one kind of important micropollutants in water which need to be removed effectively. Developing one kind of material for effectively removing SMX in water is crucial in treatment process. In this study, core–shell structured metal–organic frameworks (MOFs) with increasing shell thickness (5, 10, and 20-ZIF-8@ZIF--67 s) were selected as an ideal platform to develop water-stable hierarchical porous carbons (HPCs) using one-step calcination, showing the dual functionals of both adsorption and catalysis by producing large amount of acitve species (1O2). These novel HPCs systematically optimized at increasing temperatures and ratios of two metals. The 10-Co-NHPC-900 at optimal conditions shows highest adsorption capacities and initial adsorption rates, which are 4.56 and 10.35 times higher than those of calcinated ZIF-67 s. The decomposition mechanisms based on PMS were systematically studied by analyzing oxidant consumption, reactive oxygen species and by-products of SMX. In addition, Co ions leached amount of 10-Co-NHPC-900 was 63.6 times lower than that of MOF precursor, indicating that the cobalt-based porous carbon have higher water stabilities. This study offers an efficient approach for reducing micropollutants risk using water-stable hierarchical porous carbons.

Facile synthesis of geopolymer-based hierarchical porous materials for efficient adsorption-photocatalysis of dye wastewater

Facile synthesis of geopolymer-based hierarchical porous materials for efficient adsorption-photocatalysis of dye wastewater

Enhanced construction of 3D carbon skeleton through molten salt coupling activation effect for high efficiency capacitive deionization of lead (II) ions removal in wastewater

Efficiently eliminating of highly toxic ultra-dilute lead ions (Pb2+) from wastewater is a challenging task. Capacitive deionization (CDI) technology, based on the electrochemical capacitance mechanism, has emerged as a pivotal approach to address this challenge. In this work, a KNO3-mediated molten salt-coupled activation strategy was proposed to prepare nitrogen-doped hierarchical porous biomass carbon electrode material (3DCF-650-0.2) with a three-dimensional carbon skeleton, which was integrated into a symmetrical CDI device for Pb2+ removal. The 3DCF-650-0.2 electrode exhibited a high specific capacitance of 330.3 F g-1 at a current density of 1 A g-1, with a capacity retention rate of 98.45% after 10,000 cycles at 10 A g-1. Furthermore, the electrochemical adsorption capacity of the CDI device for Pb2+ reached 72.86 mg g-1 (1.2 V, 50 mg L-1), and the CDI device retained a high adsorption capacity of 91.14% after twenty adsorption/desorption cycles. These excellent adsorption properties are attributed to the in-situ activation and gas foaming of KNO3, which favors the production of reasonable pore structure (electric double-layer capacitance) and an appropriate pyrrolic nitrogen doping amount (selective adsorption) in the carbon materials. This work provides insight into the mechanism of the molten salt-coupled activation strategy, offering new ideas for the targeted design of high-performance CDI biomass carbon materials.

Hierarchical porous metamaterial for sound absorption

Absorption of sound is of great importance in several engineering applications, from room acoustics to engine noise reduction. Porous media are practical and commonly used to address this issue. However, their performance is limited at large wavelengths, where more material is required. Inspired by recursive patterns at multiple scale lengths, typical of many biological systems, we propose here a new design based on hierarchical multilayered porous materials. Two hierarchical designs are investigated: periodic and gradient. In both cases it is found that the increase of the hierarchy level allows to simultaneously (i) increase the absorption, and (ii) reduce the quantity of porous material required. Both the cases of normal and oblique incidences are examined. The absorption coefficient is calculated via the transfer matrix method and the finite element method, supporting measurements in an impedance tube. The porous media are described through the JCA model. An optimization algorithm based on the metaheuristic Greedy Randomized Adaptive Search Procedure is developed to optimize the organization of the porous layers, and practical tips are given on the most suitable choice of parameters (static air-flow resistivity, angle of incidence) to obtain the highest absorption amplification at desired low frequencies.

Assembly and jamming of polar additive-swollen microgels at liquid–liquid interfaces: From inverse Pickering emulsions to functional materials

HypothesisPoly-N-isopropylacrylamide (PNIPAM)-based microgels have garnered significant interest as effective soft particulate stabilizers because of their deformability and functionality. However, the inherent hydrophilic nature of microgel restricts their potential use in stabilizing water-in-oil (W/O) Pickering emulsions. Employing diverse polar additives can improve the hydrophobicity of microgels, thus unlocking new possibilities in inverse Pickering emulsion formation and materials fabrication. ExperimentsDifferent types of microgels were generated using free-radical precipitation polymerization with tailored physiochemical properties. The effect of various polar additives on the wettability, adsorption kinetics, and interfacial coverage of microgels was systematically investigated. Additive-swollen microgels were utilized to stabilize inverse W/O Pickering emulsions, which served as templates to develop functional materials with stimuli responsiveness and hierarchical structures. FindingsAdditive-swollen PNIPAM-based microgels exhibited enhanced hydrophobicity and superior emulsifying capability, which spontaneously assembled and jammed at oil–water interfaces, resulting in a significant interfacial energy decrease. The microgels formed a tightly packed, elastic, and responsive microgel monolayer. The feasibility of the strategy was verified by preparing various inverse W/O Pickering emulsions and high internal phase Pickering emulsions (HIPPEs). More importantly, this straightforward formation strategy of microgel-stabilized inverse W/O Pickering emulsions offered a novel platform to create functional materials with customized inner structures from microscale (e.g., responsive core–shell hydrogel microspheres and colloidosomes) to macroscale (e.g., hierarchical porous materials) that can be used for potential applications, such as recyclable contaminant removal and droplet manipulation.

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

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

Conductive and Cytocompatible Poly(3,4)ethylene-dioxythiophene:poly(styrenesulfonate) Hierarchical Porous Materials: From Liquid to Solid Foams

Conductive and Cytocompatible Poly(3,4)ethylene-dioxythiophene:poly(styrenesulfonate) Hierarchical Porous Materials: From Liquid to Solid Foams

Capacity building in porous materials research for sustainable energy applications.

The project aimed to develop porous materials for sustainable energy applications, namely, hydrogen storage, and valorization of biomass to renewable fuels. At the core of the project was a training programme for Africa-based researchers in (i) the exploitation of renewable locally available raw materials; (ii) the use of advanced state-of-the-art techniques for the design and synthesis of porous materials (zeolites and metal-organic frameworks (MOFs)) for energy storage; and (iii) the valorization of sustainable low-value feedstock to renewable fuels. We found that compaction of the UiO-66 MOF at high pressure improves volumetric hydrogen storage capacity without any loss in gravimetric uptake, and experimentally demonstrated the temperature-dependent dynamic behaviour of UiO-66, which allowed us to propose an activation temperature of ≤ 150°C for UiO-66. Co-pelletization was used to fabricate UiO-66/nanofibre monoliths as hierarchical porous materials with enhanced usable (i.e. deliverable) hydrogen storage capacity. We clarified the use of naturally occurring kaolin as a source of silica and alumina species for zeolite synthesis. The kaolin-derived zeolite X was successfully used as a catalyst for the transesterification of Jatropha curcas oil (from non-edible biomass) to biodiesel. We also prepared porous composites (i.e. carbon/UiO-66, organoclay/UiO-66 and zeolite/carbon) that were successfully applied in electrochemical sensing.

Synergistic enhancement of metal–organic framework-derived hierarchical porous materials towards photothermal conversion and storage properties of phase change materials

The design and synthesis of composite phase change materials that integrate photothermal conversion and latent heat storage have guiding significance for the efficient development and utilisation of solar energy. In this study, taking into consideration the advantages of metal–organic frameworks (MOFs) with adjustable structure and properties, HKUST-1-derived CuO/hierarchical porous carbon materials were employed and integrated with palmitic acid (PA) to synthesise composite phase change materials that exhibit exceptional comprehensive properties. The effects of different carbonation temperatures on HKUST-1-derived CuO/hierarchical porous carbon were analysed through a series of characterisations. The hierarchical porous structure in the blended system offers abundant pore structure and high specific surface area to prevent leakage of phase change materials. Composite phase change materials can maintain good shape stability and excellent thermal energy storage capacity. The thermal storage efficiency and photothermal conversion efficiency are 98.28% and 81.83%, respectively. Meanwhile, the thermal conductivity of the composite phase change material is 3.65 times that of pure PA. In conclusion, the MOFs derivative-based composite phase change materials designed in this study exhibited potential for thermal energy storage and can be applied to the field of solar energy conversion and storage systems.

Design of High-Performance Formyl-Functionalized COF Aerogels as Quasi-Solid Lithium Battery Electrolyte by a Solvent Substitution Strategy.

Covalent organic framework (COF) aerogels with functional groups offer exceptional processability and functionality for various applications. These hierarchical porous materials combine the advantages of COFs with the benefits of aerogels, overcoming the limitations of conventional insoluble and nonfusible COF powders. However, achieving both high crystallinity and shape retention remains a challenge for functionalized COF aerogels. In this work, we develop a novel and general solvent substitution method for the one-step synthesis of formyl-functionalized COF aerogels without harsh vacuum conditions. These aerogels exhibit excellent processing capabilities, superior mechanical strength, and enhanced functionality. As a proof-of-concept, they were used in adsorption and lithium metal battery applications, significantly maximizing the structural advantages of COFs, e.g.: (i) the hierarchical porous structure is fully wetted by the electrolyte to form continuous transport channels; (ii) the polar groups, which are easier to be acquired, help in desolvation and transfer of Li+; (iii) the regular pore structures stabilize deposition of Li+ and inhibit the growth of lithium dendrites. These combined benefits contribute to a lighter battery with improved energy density and enhanced safety.

Advances in hierarchically porous materials: Fundamentals, preparation and applications

Hierarchically porous materials have enormous potential in energy storage, thermal management, desalination, biomedicine, and catalytic reactions for their superior thermophysical properties, high specific surface area, low density, and excellent accommodation capability with volume and thermal variation. As the demand for sustainable energy solutions continues to grow, it is crucial to optimize and fabricate hierarchically porous materials that can cater to diverse application scenarios. Based on the significant progress made in recent years, this study aims to review advanced hierarchically porous materials preparation methods and engineering applications. This study first introduces the fluid flow and heat transfer mechanism in hierarchical porous materials, providing a theoretical basis for the structural design and preparation methods to improve the evaporation performance of porous materials. The study focuses on the design and preparation methods of hierarchically porous materials, including metallic materials, ceramic materials, and carbon-based materials. In addition, the application scenarios of hierarchically porous materials are introduced, and the existing challenges and prospects of the design, preparation, and application of hierarchically porous materials are explained. The review provides an attempt to investigate the potential of hierarchically porous materials to become important contributors to global renewable and sustainable energy development.

Synthesis of large mesoporous silica for efficient CO2 adsorption using coal gasification fine slag

Coal gasification fine slag (CGFS), a byproduct of the coal gasification process, is currently being recognized as a resource with significant potential for value addition and sustainable applications, especially in synthesizing CO2 adsorbents. The overarching challenges in this domain include the attainment of high-efficiency, environmentally benign transformation of CGFS into useful products, and the development of cost-effective adsorbent materials featuring precisely engineered pore structures. In this study, a hierarchical porous nanostructured silica material is synthesized rapidly, efficiently, and cost-effectively through acid leaching and alkaline dissolution-assisted hydrothermal treatment, employing CGFS as the precursor. The mass ratios of sodium hydroxide (NaOH) to CGFS range from 0.4 to 1, resulting in varying morphologies and adsorption properties. Specifically, the sample with the NaOH to CGFS ratio of 0.6 (CGFS-0.6) shows the best adsorption performance. The adsorption capacities are 2.87 mmol/g and 8.49 mmol/g at 20 °C with 15 % and 45 % CO2 concentration, respectively. The material is characterized by a well-developed pore structure shaped like a bouquet of flowers, with a specific surface area of 457 m2/g and pore volume reaching 2.34 cm3/g. During the hydrothermal processing, silicate/aluminosilicate entities self-organized into a Si-O-Na/Al network structure, endowing the synthesized adsorbent with optimal internal porosity and silanol functionalities. The adsorption equilibrium is achieved rapidly within 10 min, and CO2 adsorption stability remains robust across 20 successive cycles. All isothermal models of the adsorbents conform to the Sips model. This study offers a promising pathway for the value-enhanced utilization of coal-derived solid wastes.

In Situ Self-Assembly of Nitrogen-Doped 3D Flower-like Hierarchical Porous Carbon and Its Application for Supercapacitors.

The hierarchical porous carbon-based materials derived from biomass are beneficial for the enhancement of electrochemical performances in supercapacitors. Herein, we report the fabrication of nitrogen-doped 3D flower-like hierarchical porous carbon (NPC) assembled by nanosheets using a mixture of urea, ZnCl2, and starch via a low-temperature hydrothermal reaction and high-temperature carbonization process. As a consequence, the optimized mass ratio for the mixture is 2:2:2 and the temperature is 700 °C. The NPC structures are capable of electron transport and ion diffusion owing to their high specific surface area (1498.4 m2 g-1) and rich heteroatoms. Thereby, the resultant NPC electrodes display excellent capacitive performance, with a high specific capacitance of 249.7 F g-1 at 1.0 A g-1 and good cycling stability. Remarkably, this implies a superior energy density of 42.98 Wh kg-1 with a power density of 7500 W kg-1 in organic electrolyte for the symmetrical supercapacitor. This result verifies the good performance of as-synthesized carbon materials in capacitive energy storage applications, which is inseparable from the hierarchical porous features of the materials.

Investigating antimicrobial behavior of thymol/Zn encapsulated hierarchically structured zeolite and thymol release kinetics

A new bioactive material was proposed by encapsulating thymol molecules and Zn2+ cations within the post-modified intracrystalline voids of hierarchical zeolite X crystals. To enhance the accessibility of thymol molecules within zeolite X crystals, commercial zeolite samples underwent post-synthesis treatment involving consecutive aqueous KCl, NH4Cl, and Na2H2EDTA solutions. The gas adsorption method utilized the encapsulation of both Zn2+ cation and thymol molecules into the resulting hierarchical zeolite X framework, which demonstrated improved antimicrobial activity. While sole thymol-encapsulated zeolite X exhibited no antimicrobial activity against S. aureus, Zn2+ encapsulated zeolite X (ZnX), thymol encapsulated post-treated zeolite X (HX-thy), and both Zn2+ and thymol encapsulated post-treated zeolite X (ZnHX-thy) displayed zone of inhibition values of 18.7 mm, 25.0 mm, and 37.5 mm, respectively. Adding Zn2+ and creating a hierarchical pore system in the zeolite X framework altered the release profiles. The Higuchi kinetic release model has the highest R2 value to describe the process of thymol release from X-thy, whereas the Elovich release model has the best fitting profile of thymol release kinetics from ZnX-thy, HX-thy, and ZnHX-thy. Results indicate that thymol and Zn2+ containing hierarchical porous materials could be beneficial tools for obtaining enhanced antibacterial activity and stability with reduced degradation and volatility of thymol with extended protection against microbial attack due to the controlled release. These findings highlight an innovative approach to designing sustainable and green materials, utilizing modified porous networks that encapsulate natural antibacterial compounds with environmentally benign metal ions.

Modulation of metal-organic frameworks by anionic surfactants for rapid adsorption of organic pollutants bisphenol A and chrome black T

With the accelerated development of industry, which generates large quantities of sewage discharged into the aquatic environment, serious impacts on both environmental and human health. Detecting various organic contaminants in water sources has become common, presenting huge challenges for water treatment. Metal-organic frameworks are characterized by their rich porous structures and high chemical activity, making them ideal adsorbents for removing organic pollutants from water. In this study, sodium dodecylbenzene sulfonate is added to the precursor solution of MIL-101(Cr)-Cl2 and synthesized hierarchical porous structure adsorbents MIL-SDBS-X, using hydrothermal synthesis to enhance their adsorption capacity, making efficient and rapid removal of bisphenol A(BPA) and chromium black T(EBT), two common organic pollutants in water, which MIL-SDBS-0.7 was the most effective. MIL-SDBS-0.7 exhibites great potential in the adsorption of BPA and EBT for its high adsorption capacity (260.5 mg-1·g-1 and 272.3 mg-1·g-1) and rapid adsorption (equilibrium could be achieved in 15 minutes), The findings reveal adsorption kinetics aligns with the pseudo-second-order model and the Langmuir equation best fits to study adsorption of MIL-SDBS-0.7 to BPA and EBT. Thermodynamic parameters affirm the exothermic and higher spontaneity behavior of the adsorption process. Moreover, the adsorption mechanism of MIL-SDBS-0.7 was explored, illustrating the crucial roles of effects of hydrogen bonding π-π stacking and pore filling in the adsorption of BPA and EBT. Therefore, this work not only provided a convenient strategy for the preparation of efficient and fast MIL-SDBS-0.7 hierarchical porous material but also highlighted the promising potential of synthesized absorbents as an effective adsorbent for organic pollutants in wastewater treatment and environmental remediation.

Enhancement of zinc-ion storage capability by synergistic effects on dual-ion adsorption in hierarchical porous carbon for high-performance aqueous zinc-ion hybrid capacitors

Aqueous zinc-ion capacitors (AZICs) are considered potential energy storage devices thanks to their ultrahigh power density, high safety, and extended cycling life. Carbon-based materials widely used as cathodes in AZICs face challenges, such as inappropriate pore sizes, poor electrolyte–electrode wettability, and insufficient vacancy defects and active sites. These limitations hinder efficient energy storage capacity and long-term stability. To address these issues, the B and F co-doped hierarchical porous carbon cathode materials (BFPC) are constructed through a facile annealing treatment process. The BFPC-2//Zn device exhibited high capacities of 222.4 and 118.3 mAh g−1 at current densities of 0.2 and 10 A g−1, respectively. Notably, the BFPC-2//Zn device demonstrated long-term cycling stability with a high capacity retention of 96.9 % after 20,000 cycles at 10 A g−1. Additionally, the assembled BFPC-2 based AZICs displayed a maximum energy density of 175.8 Wh kg−1 and an ultrahigh power density of 17.3 kW kg−1. Mechanism studies revealed that the exceptional energy storage ability and charge-transfer process of the BFPC cathode are attributed to the synergistic effect of B and F heteroatoms and the coupling effect between vacancy defects and pore size. This work presents a novel design strategy by incorporating B and F active sites into hierarchical porous carbon materials, providing enhanced energy storage capabilities for practical application in AZICs.

Hierarchical-porous acoustic metamaterials: A synergic approach to enhance broadband sound absorption

A novel design for hierarchical-porous acoustic metamaterials (HPAM) is proposed to enhance the functionality of Helmholtz-type resonators and porous materials, achieving continuous and efficient broadband sound absorption. This method can potentially eliminate absorption valley and improve the coupling strength through a synergistic energy dissipation mechanism and hybrid impedance matching behavior. Excellent sound-absorbing capability of the elaborately crafted HPAM was demonstrated analytically, numerically, and experimentally. Specifically, the results revealed an impressive average absorption coefficient of 0.77, with 73 % of the α points exceeding 0.8 across the entire test frequency range. Furthermore, the sound absorption of HPAM can be further optimized to attain ultra-broadband properties by modifying the hierarchical configuration and composite design of the porous materials. The physical mechanism is revealed through the integration of the hierarchical scaling effect and the energy-trapped mode. Numerical simulations revealed the emergence of three distinct absorption peaks at frequencies of 0.76, 1.4, and 3.6 kHz, respectively, and the effective absorption spectrum exceeded 3.4 kHz. Overall, the proposed design highlights the role of hierarchical structures and porous materials in synthesizing superior sound-absorbing properties that fullyelucidate the relationship between structure and performance,and provide an avenue for potential noise-control applications.

Macrocycle-on-COF photocatalyst constructed by in-situ linker exchange for efficient photocatalytic CO2 cycloaddition

Functionalizing macrocycle with gas capture and catalytic ability onto covalent organic frameworks (COFs) can generate hierarchical porous materials with enhanced properties, while the challenge is how to improve full utilization of the active sites and maintain the crystallinity of the parent framework. Herein, we developed a “Macrocycle-on-COF” strategy by partial in-situ linker exchange to gain core-shell hybrids containing hierarchical pores. We demonstrated that the macrocycle-on-COF with functionalized pillar[5]arene have a profound effect on highly CO2 adsorption and abundant active sites. The photoelectrical measurement showed that the macrocycle-on-COF was an excellent photocatalyst with fast photoresponse and superior charge separation efficiency. With the assistance of light, the functionalized OH-P[5]-on-COF achieves efficient photocatalytic CO2 cycloaddition reaction under ambient conditions (20 °C and 1 atm), in which a 99% conversion can be achieved within 3 h and the performance is superior compared to previously reported COFs. This study presents the first example of using COFs as photocatalysts for photocatalytic CO2 cycloaddition reaction under ambient conditions.

3D-Printing of Hierarchical Porous Copper-Based Metal-Organic-Framework Structures for Efficient Fixed-Bed Catalysts.

Metallic structures with hierarchical open pores that span several orders of magnitude are ideal candidates for various catalyst applications. However, porous metal materials prepared using alloy/dealloy methods still struggle to achieve continuous pore distribution across a broad size range. Herein, we report a printable copper (Cu)/iron (Fe) composite ink that produces a hierarchical porous Cu material with pores spanning over 4 orders of magnitude. The manufacturing process involves four steps: 3D-printing, annealing, dealloying, and reannealing. Because of the unique annealing process, the resulting hierarchical pore surface becomes coated with a layer of Cu-Fe alloy. This feature imparts remarkable catalytic ability and versatile functionality within fixed bed reactors for 4-nitrophenol (4-NP) reduction and Friedländer cyclization. Specifically, for 4-NP reduction, the porous Cu catalyst demonstrates an excellent reaction rate constant (kapp = 86.5 × 10-3 s-1) and a wide adaptability of the substrate (up to 1.26 mM), whilst for Friedländer cyclization, a conversion over 95% within a retention time of only 20 min can be achieved by metal-organic-framework-decorated porous Cu catalyst. The utilization of dual metallic particles as printable inks offers valuable insights for fabricating hierarchical porous metallic structures for applications, such as advanced fixed-bed catalysts.

Breaking the diffusion coefficient limitation of bismuth oxide anodes for aqueous alkaline batteries with ultra-high rate capability

In this study, the double-high hierarchical porous amorphous Bi2O3 anode material (HPAM Bi2O3) is firstly synthesized by ion exchange strategy via employing Bi-BTC nanorod as the precursor.