Hierarchical Porous Metal Research Articles

Boronate affinity metal–organic frameworks molecularly imprinted membranes with hierarchical porous channels for the selective separation of naringin

Naringin (NRG), known as an important natural flavoniod compounds, exhibits excellent phamaceutical value and clinical application prospect. However, the main obstacle to the isolation and purification of NRG is the low concentration and complexity of the extraction system. Herein, a new kind of hierarchical porous metal–organic frameworks (MOFs) based molecularly imprinted membranes (PBMMA-MIMs) for the specific separation of NRG. The prepared PBMMA-MIMs showed the fast adsorption kinetics (within 120 min). Moreover, the abundant boronic acid imprinted recognition sits and hydrophilic hierarchical porous MOFs improved the adsorption capacity (the maximum adsorption amounts 57.39 μmol/g) and exhibited selective NRG adsorption (imprinting factor 2.31) with efficiency over 91.69 % after seven adsorption–desorption cycles. In addition, the coarse NRG could be effectively extracted to a promising purity of 93.13 % via PBMMA-MIMs. This study provides new insights into the design molecularly imprinted membranes via environmentally friendly synthesis route for the preparation for enriching high-value flavoniods, achieving efficient purification rate of agricultural wastes for pollution control, and promoting the sustainable reuse in complex agricultural wastewater.

Morphology evolution and mechanism of massive three-level hierarchically porous silver fabricated by vapor phase dealloying

In this study, the Gasar process and vapor phase dealloying (VPD) method were combined to fabricate a massive three-level hierarchical porous silver (MTHPS), which composed of interconnected micron-sized, submicron-sized, and nanoporous structures. The key aspect of this study lies in the preparation of a hypoeutectic Gasar Mg91.6Ag8.4 alloy with the regular micron-scale pore structure as the dealloying precursor, improving the size of the hierarchical porous metal. Under high vacuum conditions, by adjusting the dealloying time and temperature, MTHPS samples with various morphologies were obtained. After dealloying, the MTHPS exhibited Gasar pores (diameter 376 ± 86 μm), submicron pores (diameter 465 ± 125 nm), and a continuous ligament/channel structure (pore size less than 70 ± 40 nm). The coarsening index was 3.6258, and the activation energy was measured to be 0.95 eV, indicating that the formation and coarsening of the pores during VPD are attributed to surface diffusion. The calculated evaporated mass of the precursor alloy after dealloying was very close to the experimental value (±0.004 g), indicating that the evaporation of Mg occurred simultaneously in both solid and liquid phases during the VPD process. This study elucidates the phase transformation characteristics, structural control, and diffusion mechanisms of MTHPS prepared by VPD, providing valuable insights for further research and applications of MTHPS.

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.

Metal-organic framework gel derived magnetic hierarchical porous Fe-N-C catalyst as peroxymonosulfate activator for efficient degradation of amoxicillin via singlet oxygen-dominated nonradical pathway

The rational design of transition metal and nitrogen co-doped carbon-based catalysts for the efficient removal of antibiotics through non-radical pathway of peroxymonosulfate (PMS) activation has attracted widespread attention. Herein, a magnetic hierarchical porous Fe-N-C catalyst (FeBDC-NH2-800) was successfully constructed by pyrolyzing the hierarchical porous precursor metal–organic framework gel (FeBDC-NH2) consisting of nitrogen-containing ligands. Benefiting from the defective heterojunction structure, the catalyst exhibited effective and efficient degradation towards amoxicillin (AMX) by activating PMS to produce 1O2. The degradation of AMX was up to 97.4 % within 30 min, which was 2.48 and 2.16 times more than that of FeBDC-NH2/PMS and nanosized Fe3O4/PMS respectively. The high degradation performance could be maintained toward low pollutant concentration conditions and cycle experiments, manifesting its possibility for practical application. Combining the data of quenching experiments, electron spin resonance spectra, electrochemical experiments, X-ray photoelectron spectra and density functional theory calculation, the mechanism was revealed that radical pathway contributed little during degradation while singlet oxygen played a significant role. The cleavage of lattice oxygen and defective heterogeneous structure of FeBDC-NH2-800 contributed together to promote PMS for 1O2 production.

Facile Construction of Stable Hierarchical Porous Metal–Organic Frameworks for In Situ Immobilization of β-Glucosidase Based on Competitive Coordination and Selective Etching Strategies

Facile Construction of Stable Hierarchical Porous Metal–Organic Frameworks for In Situ Immobilization of β-Glucosidase Based on Competitive Coordination and Selective Etching Strategies

Trimodal Hierarchical Porous Metal–Organic Frameworks with Tunable Mesoporous Core–Shell Architectures

Trimodal Hierarchical Porous Metal–Organic Frameworks with Tunable Mesoporous Core–Shell Architectures

Hierarchical porous metal organic framework aerogel for highly efficient CO2 adsorption

Sustainable low-carbon economy has attracted global attention, and the development of advanced CO2 capture technology has become an important undertaking. Metal organic frameworks (MOFs) featured with high specific surface area and large porosity have held the promise for CO2 adsorption, but the micron scale make them difficult to handle, leading to easily be blown away, pipeline blockage, and the decline of adsorption capacity. Here, we demonstrate a novel strategy to develop a nanoporous HKUST-1 aerogel with hierarchical pore structure by combining HKUST-1 and aramid nanofiber for promoting CO2 adsorption. The resultant HKUST-1 aerogel has a low density of 5.86 mg/cm3, high specific surface area of 636.62 m2g−1, and hierarchical porosity of 99.33 %. The meso-/macropores of HKUST-1 aerogel can act as gas transfer channels to facilitate the transport CO2 into the HKUST-1, and the micropores of HKUST-1 provide active sites for CO2 adsorption. Benefitting from the synergistic effect of the hierarchical pore structure, the HKUST-1 aerogel demonstrates high CO2 adsorption capacity of 7.29 mmol/g, and high adsorption selectivity of 39 for CO2/N2 and 42 for CO2/O2. This novel design may provide a reliable theoretical and experimental basis for the development of MOF aerogel as CO2 adsorbent candidate for environmental purification.

Macro‐/mesoporous Metal–Organic Frameworks Templated by Amphiphilic Block Copolymers Enable Enhanced Uptake of Large Molecules

AbstractThe first synthesis of hierarchical porous metal–organic frameworks (HP‐MOFs) is reported through a solvent evaporation‐induced co‐assembly of polystyrene‐block‐poly(ethylene oxide) (PS‐b‐PEO) and MOF building blocks. The growth of MOFs is restricted to confined spaces formed by self‐assembled PS‐b‐PEO, and mesopores and/or macropores are created after removing PS‐b‐PEO by solvent rinsing. This approach avoids phase separation and competitive interactions between templates and MOF building blocks. Both amorphous and crystalline HP‐MOFs can be synthesized by finely controlling MOF growth conditions. Additionally, HP‐MOFs (ZIF‐L sheets) with honeycomb‐like channels show significantly enhanced incorporation of large guest molecules compared to microporous MOFs. This study establishes an efficient synthetic strategy for preparing HP‐MOFs with highly accessible mesopores and macropores for applications involving large molecules.

Metal oxyacid salts-confined pyrolysis towards hierarchical porous metal oxide@carbon (MO@C) composites as lithium-ion battery anodes

Metal oxyacid salts-confined pyrolysis towards hierarchical porous metal oxide@carbon (MO@C) composites as lithium-ion battery anodes

Fabrication of Hierarchical Porous Metal Oxides by the HPMC-Assisted Gel Combustion Strategy: Incorporation of Nanoceria into Cookie-like Mn2O3 with Enhanced Oxidation Activity and Excellent Water Resistance

Constructing nonprecious metal oxide catalysts with a hierarchical porous structure by a simple method for the deep catalytic oxidation of toxic volatile organic compounds at low temperatures is of great value and significance. In this work, a porous manganese trioxide catalyst (Mn2O3-H) was prepared by a hydroxypropyl methylcellulose-assisted combustion synthesis strategy for catalytic complete oxidation of gaseous toluene. Benefiting from the rich porous nanostructure, Mn2O3-H has much higher specific surface area and active site density, resulting in better low-temperature reducibility and oxygen activation ability than blank Mn2O3 formed by direct calcination. With this sol–gel combustion process, CeO2 nanoparticles could be successfully introduced to form cookie-like Ce–Mn composite oxide with a hierarchical porous nanostructure, which builds the strong interaction of CeO2–Mn2O3 to weaken Mn–O with more active defects. Among Ce-doped catalysts, 5%CeMn-H shows the best catalytic activity in toluene oxidation with 90% conversion temperature at 242 °C under a weight hour space velocity of 60,000 mL·g–1·h–1, which is about 30 and 133 °C lower than that of Mn2O3-H and Mn2O3-B, respectively. This advantage is also shown in other typical hydrocarbons such as propylene and propane. Moreover, the as-prepared Ce-doped catalyst exhibits excellent stability and water resistance ability. This simple robust sol–gel combustion method will provide valuable enlightenment for designing porous catalysts with high performance for related catalytic reactions.

Nanoporous Zeolitic Imidazolate Framework-8 Nanoparticles for Arsenic Removal

Herein, we report a solvent-free self-templating strategy for rapid synthesis of nanoscale hierarchically porous zeolitic imidazolate framework-8 (HP-ZIF-8) with micro-, meso-, and macropores. ZIF-8 crystals were produced in situ on ZnO nanoparticles via vapor deposition of 2-methylimidazole, and hierarchical nanopores were obtained after selectively etching ZnO. ZnO nanoparticles acted as both a Zn source and a meso-/macropore template for HP-ZIF-8. Systematic arsenic adsorption experiments showed that the presence of meso-/macropores can effectively enhance and accelerate arsenic removal via chemisorption. As a result, HP-ZIF-8 exhibited an As(III) adsorption capacity of 104.9 mg/g, nearly double that of traditional ZIF-8 nanoparticles, despite having remarkably more micropores. This study provides a highly adsorbable strategy to fabricate hierarchical porous metal–organic frameworks for pollutant removal.

Sulfidation and NaOH etching in CoFeAl LDH evolved catalysts for an efficient overall water splitting in an alkaline solution.

In this study, a hierarchical interconnected porous metal sulfide heterostructure was synthesized from CoFeAl layered double hydroxides (LDHs) by a two-step hydrothermal process (sulfidation and a NaOH etching process). Among the as-made samples, the CoFeAl-T-NaOH electrode exhibited excellent oxygen and hydrogen evolution reaction catalytic activities with overpotentials of 344 mV and 197 mV at the current density of 100 mA cm-2, respectively. Meanwhile, small Tafel slopes of 57.7 mV dec-1 and 106.5 mV dec-1 for water oxidation and hydrogen evolution were observed for the CoFeAl-T-NaOH, respectively. Serving as both the cathode and anode for overall water splitting, the CoFeAl-T-NaOH electrode reached a current density of 10 mA cm-2 at a cell voltage of 1.65 V with excellent stability. The enhanced electrocatalytic activity could be attributed to: the hierarchical interconnected nanosheet structure facilitating mass transport; the porous structure promoting electrolyte infiltration and reactant transfer; the heterojunction accelerating charge transfer; and the synergistic effect between them. This study offered a new clue for in situ synthesizing porous transition-metal based heterojunction electrocatalysts with a careful tuning of the sequence of sulfuration and alkaline etching to enhance the electrocatalytic performance.

A new ligand-regulated strategy of highly mesoporous metal–organic framework assembled in ionic liquid/ethanol solvent

The hierarchical porous metal–organic frameworks catalysts were synthesized by ligand regulation in ionic liquid/ethanol system for the first time. The porosity and morphology could be tuned by the mass fraction...

Co@ZIF‐8/TiO2 heterojunction for green hydrogen generation

A wet‐incipient impregnation method was reported to synthesize hierarchical porous bimetallic (Co, Zn)‐zeolitic imidazolate frameworks (ZIF‐8)/TiO2 (Co@ZIF‐8/TiO2) for green hydrogen generation via photocatalytic water splitting. Co@ZIF‐8/TiO2 showed higher photocatalytic efficiency than TiO2, with a hydrogen generation rate (HGR) of 13 mmol·h−1·g−1 with a 151‐fold increase in the catalytic performance of TiO2. The photocatalytic HGR of Co@ZIF‐8/TiO2 was superior to that of the ZIF‐8/TiO2 heterostructure. Co@ZIF‐8 showed a hierarchical porous structure containing micropores and mesopores regimes, providing a proficient transport channel for charge transfer. This study presents new prospects for using hierarchical porous metal–organic frameworks (MOFs) as support and promoter in photocatalytic applications of semiconductor such as TiO2.

Tuning the Architecture of Hierarchical Porous CoNiO2 Nanosheet for Enhanced Performance of Li-S Batteries

As the desired components and crystal structure of a transition metal oxide catalyst are selected, architecture is a dominating factor affecting its electrocatalytic performance for applications in lithium-sulfur (Li-S) batteries. Nano-compounds with a hollow architecture are undoubtedly the ideal catalysts for enhancing cathodic performance for more exposed active sites and shortened path lengths than are other architectures. Additionally, the internal stress in hollow architecture is favorable for further performance enhancement, due to its regulation effects of driving the d-band center of the transition metal in the active sites to migrate toward the Fermi level, which will promote the chemical adsorption and catalytic conversion of the polysulfides (PSs). To this point, we select hierarchical porous dual transition metal oxide CoNiO2 nano-boxes (CoNiO2(B)) as the conceptual model; meanwhile, CoNiO2 nano-flakes (CoNiO2(F)) with identical stoichiometry and crystal structure are also analyzed as a comparison. Li-S batteries based on CoNiO2(B) deliver superior energy storage features, including a reversible discharge capacity of 1232 mAh g−1 at 0.05 C and a stable cycle performance with decay rate of 0.1% each cycle even after 300 cycles at 1 C. This research presents an alternative scheme for booting the performance of Li-S batteries.

Using surface-modified UiO-66 with hierarchical pores to pack polyethylene glycol for phase change thermal energy storage: Experiment and molecular dynamics simulations

High performance composite phase change materials (PCMs) act a pivotal part in energy saving and renewable energy development as well as utilization. Herein, hierarchical porous metal–organic framework (MOF) UiO-66-CH3 with a high specific surface area (1086 m2/g) and large pore volume (1.22 cm3/g) was prepared to pack polyethylene glycol 2000 (PEG) organic PCM. The thermal property and stability of the synthesized composite PCMs were explored, and the mechanism was further analyzed by performing molecular dynamics (MD) simulations from an atomic view. The maximum loading of PEG/UiO-66-CH3 is 65 wt%, which is 62.5 % higher than that of single-scale microporous UiO-66. The crystallization ratio of PEG/UiO-66-CH3 exceeds 70 %. MD results prove that in hierarchical porous frameworks, the smaller pores prevent the leakage of PCMs, while the larger pores increase the adsorption of PCMs. Besides, the supercooling degree of PEG/UiO-66-CH3 decrease by 48 % than that of pure PEG, benefiting from the large specific surface area of UiO-66-CH3, which can provide a large number of heterogeneous nucleation sites for PCM. The simulation results reveal that the heat conduction property of UiO-66 and PEG was not affected by the compounding. The thermal conductivity of PEG/UiO-66-CH3 (0.496 W/(m·K)) is 32 % higher than that of SA/Cr-MIL-101-NH2 MOF-based material, while is 107 % higher than that of single-scale mesoporous PEG/MCM-41 composite. The composite PCM shows good thermal stability after 50 times thermal cycling. This work provides theoretical guidance for the synthesis of functional hierarchical porous composite PCMs with excellent thermal storage performance.

Mechanistic Principles for Engineering Hierarchical Porous Metal–Organic Frameworks

Metal-organic frameworks (MOFs) have generated tremendous research interest in the past two decades, due to their high surface areas, tailorable active sites, and tunable structures. Hierarchical porous MOFs (HP-MOFs) with two or more pore systems are particularly attractive, benefiting from improved active site accessibility and enhanced mass diffusivity in applications involving bulk molecules. This review outlines the mechanistic principles used for the rational design of HP-MOFs, current techniques used to measure their hierarchical porosities, as well as their emerging applications. We then critically summarize the current challenges in this field and provide a contemporary perspective on the technological innovations that would address current synthetic challenges in the field of HP-MOFs. The aim of this review is to provide an in-depth understanding of the formation mechanisms, materials chemistry, and structural and chemical properties of HP-MOFs while exploring ways to enhance the performance of current MOF materials in a range of fields.

Investigate the role of V in the Nitrogen-doped hierarchical porous carbon-supported binary transition metal nitrides catalyst for oxygen reduction reactions

N-doped carbon-supported titanium nitride (TiN/NC) is considered promising for its application in Zn-air batteries. However, the performance of TiN/NC cannot meet the practical application. To solve this problem, the catalytic activity and stability of the catalyst can be improved by introducing the second metal element V. In this paper, a high-performance catalyst (TixV1−xN/NC/C) was prepared by supporting titanium-vanadium binary transition metal nitride nanoparticles on nitrogen-doped carbon. The experimental results and density functional theory (DFT) calculations confirm that the electronic, atomic and microstructure of titanium nitride nanoparticles can be properly tuned by introducing V ions, which is beneficial to tune the adsorption/adsorption of oxygen intermediates on titanium nitride nanoparticles and decreasing the potential of the rate determining step, thereby increasing the catalytic activity. The TixV1−xN/NC/C composite exhibits excellent ORR performance with an onset potential (Eonset) and limiting current density of 0.91 V (vs. RHE) and 4.90 mA∙cm−2, respectively. The Ti0.85V0.15N/NC/C-based Zn-air battery exhibits the power density of 124.78 mW·cm−2, open circuit voltage of 1.34 V and high specific capacity of 731.38 mAh·g−1. More importantly, this work has deepened the understanding of the TMN-based catalytic mechanism and paved the way for enhancing the catalytic performance of TMN-based catalysts.

Wheat-like Co3O4 on carbon derived from silk as anode materials for enhanced lithium storage

The design and preparation of hierarchical porous transition metal oxide-carbon matrix anodes with unique structure play the significant role in highly reversible lithium ion batteries. Herein, hierarchical porous wheat-like Co3O4 on carbon derived from natural silk (named as SK@Co3O4) nanobelts are fabricated successfully by one-step hydrothermal technique and ensuing high-temperature calcination. The wheat-like SK@Co3O4 nanobelts consist of a number of nanobeams. The length of nanobelts is around 1 µm whereas the diameter is 200 nm. Moreover, the SK@Co3O4 anode for lithium ion batteries retains 1108 mA h g−1 following 100 cycles at 100 mA g−1, 707 mA h g−1 and 709 mA h g−1 after 150 cycles at 2 A g−1, 625 mA h g−1 and 617 mA h g−1 after 150 cycles at 5 A g−1,which show extraordinary cycle stability of the composite. The remarkable lithium storage property results from the hierarchical porous structure and this structure can not only provide a short ion transport path but also raise the area of contact between the electrolyte and electrode.

Synergistic effects of hierarchical porous structure, acidity and nickel metal for hydro-liquefaction of thermal extracts from lignite over Ni/ZSM-5

Abstract Hydro-liquefaction of the thermal extracts (HPC) from lignite was investigated over ZSM-5 and Ni/ZSM-5 with hierarchical pores or not. The thermal extracts dissolved (HPC-S) and deposited (HPC-D) at room temperature were prepared to compare their hydro-liquefaction performances. Combined to the hydrogenation properties of ZSM-5 and Ni/ZSM-5 catalysts for tetralin as a model compound, the roles of the porous structure, acidity and hydrogenation component in Ni/ZSM-5 for hydro-liquefaction of HPC were investigated. A synergy of the porous structures, nickel metal and acidity for hydro-liquefaction of HPC-S over Ni/ZSM-5 catalyst was found. During hydro-liquefaction, it is essential for the presence of nickel in the catalyst, since the parts of the benzene rings in HPC-S are first saturated by hydrogen under the role nickel. Then a certain acidity especially Brønsted acid is required in the catalyst to open the saturated benzene rings. Since there are the macromolecular organic compounds in the HPC-S, the hierarchical porous structures are required in the catalyst to promote the hydro-liquefaction performance due to their improvement on the mass transfer diffusion efficiency.