Tunable Pore Structure Research Articles

Molecular Weaving Towards Flexible Covalent Organic Framework Membranes for Efficient Gas Separations.

Covalent organic frameworks (COFs) exhibit considerable potential in gas separations owing to their remarkable stability and tunable pore structures. Nevertheless, their application as gas separation membranes is hindered by limited size-sieving capabilities and poor processability. In this study, we propose a novel molecular weaving strategy that combines hydroxyl polymers and 2D TpPa-SO3H COF nanosheets, achieving high gas separation efficiency. Driven by the strong electrostatic interactions, the hydroxyl chains thread through the COF pores, effectively weaving and assembling the composites to achieve exceptional flexibility and high mechanical strength. The penetrated chains also reduce the effective pore size of COFs, and combined with the "secondary confinement effect" stemming from abundant CO2 sorption sites in the channels, the PVA@TpPa-SO3H membrane demonstrates a remarkable H2 permeance of 1267.3 GPU and an H2/CO2 selectivity of 43, surpassing the 2008 Robson upper bound limit. This facile strategy holds promise for the manufacture of large-area COF-based membranes for small-sized gas separations.

Molecular Weaving Towards Flexible Covalent Organic Framework Membranes for Efficient Gas Separations

AbstractCovalent organic frameworks (COFs) exhibit considerable potential in gas separations owing to their remarkable stability and tunable pore structures. Nevertheless, their application as gas separation membranes is hindered by limited size‐sieving capabilities and poor processability. In this study, we propose a novel molecular weaving strategy that combines hydroxyl polymers and 2D TpPa−SO3H COF nanosheets, achieving high gas separation efficiency. Driven by the strong electrostatic interactions, the hydroxyl chains thread through the COF pores, effectively weaving and assembling the composites to achieve exceptional flexibility and high mechanical strength. The penetrated chains also reduce the effective pore size of COFs, and combined with the “secondary confinement effect” stemming from abundant CO2 sorption sites in the channels, the PVA@TpPa−SO3H membrane demonstrates a remarkable H2 permeance of 1267.3 GPU and an H2/CO2 selectivity of 43, surpassing the 2008 Robson upper bound limit. This facile strategy holds promise for the manufacture of large‐area COF‐based membranes for small‐sized gas separations.

Metal–Organic Frameworks and Derivative Materials in Perovskite Solar Cells: Recent Advances, Emerging Trends, and Perspectives

The power conversion efficiency (PCE) of perovskite solar cells (PSCs) has reached an impressive value of 26.1%. While several initiatives such as structural modification and fabrication techniques helped steadily increase the PCE and stability of PSCs in recent years, the incorporation of metal–organic frameworks (MOFs) in PSCs stands out among other innovations and has emerged as a promising path forward to make this technology the front‐runner for realizing next‐generation low‐cost photovoltaic technologies. Owing to their unique physiochemical properties and extraordinary advantages such as large specific surface area and tunable pore structures, incorporating them as/in different functional layers of PSCs endows the devices with extraordinary optoelectronic properties. This article reviews the latest research practices adapted in integrating MOFs and derivative materials into the constituent blocks of PSCs such as photoactive perovskite absorber, electron‐transport layer, hole‐transport layer, and interfacial layer. Notably, a special emphasis is placed on the aspect of stability improvement in PSCs by incorporating MOFs and derivative materials. Also, the potential of MOFs as lead absorbents in PSCs is highlighted. Finally, an outlook on the critical challenges faced and future perspectives for employing MOFs in PSCs in light of the commercialization of PSCs is provided.

Direct-through channels of ZIF-8 composite membranes via in-situ PolyBMA sealing: Radical-induced phase transformation and dye removal efficiency

Metal-organic frameworks (MOFs)-based hybrid composite membranes are promising candidates for achieving highly efficient water purification. In this study, a facile, novel pressure-induced filtration method involving in-situ polymerization of butyl methacrylate (BMA) was proposed for sealing ZIF-8 nanoparticles on top of polyethersulfone (PES) ultrafiltration membrane support. The developed (ZIF-8+polyBMA)/PES composite membranes with thin toplayers of <1 μm present attractive water permeance (up to 31 LMH/bar) and good rejection of Congo red (99.2 %) and Methylene blue (99.1 %). The ZIF-8 particles served as direct-through channels with superior separation performance due to their high porosity and tunable pore structure, while the interstices were successfully sealed with polyBMA by in-situ polymerization, as demonstrated by SEM and dye removal experiments. It was found that the morphology of ZIF-8 transformed from a rhombic dodecahedron to two-dimensional hexagonal nanosheets during the fabrication process. We hypothesize that this surprising phenomenon is caused by the reaction of the initiators (Na2S2O5 and K2S2O8) that generate the hydroxyl and sulfate radicals attacking and transforming the Zn-MIM bond network of ZIF-8. However, insights into the structural changes need to be further investigated to understand the mechanism involved.

A molecular-chemistry-manipulation strategy toward functional lignin-based porous carbon nanospheres with tunable-pore structure

Porous carbon nanospheres derived from biomass materials have inspired numerous interests in various areas. Nevertheless, their fabrications mainly depend on template-assisted or chemical activation routes. Here, a molecular-chemistry-manipulation strategy was proposed innovatively by taking advantage of the heterogeneous self-condensation characters of lignin molecules under thermal stimulation, opening a practical and versatile synthetic platform for the construction of lignin-based hierarchical porous carbon nanospheres (LHPCS). We can manipulate the condensed kinetics by tuning the environmental variables and forming designated nanospheres with inhomogeneous molecular chemistry. This intraparticle difference could provide a possibility to tune its refined structure for synthesizing hierarchical porous carbon nanospheres. Such LHPCS behaved the specific surface area of 962 m2 g−1 and pore volume of 0.76 cm3 g−1, as well as regulable pore ratios (15.5–22.9 % of macropore, 12.7–37 % for mesopore and 45–68.9 % for micropore). Besides, the monodisperse spherical morphology with hierarchical interleaved channels affords them excellent performance in optical management and energy storage, including pore-determined photothermal properties, extremely low reflectance of ca. 1.9 %, stable multi-angles specular reflectance, and anti-self-discharge induced by charge rearrangement. Our proposed molecular chemistry strategy provides an alternative pathway for constructing gradient and adjustable pore structures.

Insights into the Biological Activity and Bio-Interaction Properties of Nanoscale Imine-Based 2D and 3D Covalent Organic Frameworks.

Covalent Organic Frameworks (COFs) emerged as versatile materials with promising potential in biomedicine. Their customizable functionalities and tunable pore structures make them valuable for various biomedical applications such as biosensing, bioimaging, antimicrobial activity, and targeted drug delivery. Despite efforts made to create nanoscale COFs (nCOFs) to enhance their interaction with biological systems, a comprehensive understanding of their inherent biological activities remains a significant challenge. In this study, a thorough investigation is conducted into the biocompatibility and anti-neoplastic properties of two distinct imine-based nCOFs. The approach involved an in-depth analysis of these nCOFs through in vitro experiments with various cell types and in vivo assessments using murine models. These findings revealed significant cytotoxic effects on tumor cells. Moreover, the activation of multiple cellular death pathways, including apoptosis, necroptosis, and ferroptosis is determined, supported by evidence at the molecular level. In vivo evaluations exhibited marked inhibition of tumor growth, associated with the elevated spontaneous accumulation of nCOFs in tumor tissues and the modulation of cell death-related protein expression. The research contributes to developing a roadmap for the characterization of the intricate interactions between nCOFs and biological systems and opens new avenues for exploiting their therapeutic potential in advanced biomedical applications.

Highly Bioadaptive Scaffolds with Tuned Porous Structure Templated by Xylan Nanocrystal High Internal Phase Pickering Emulsions.

Fabrication of traditional 3D cell culturing scaffolds requires synthetic polymers or additives, posing a risk of poor biocompatibility and low biodegradability. Pickering emulsions stabilized by biobased nanomaterials can be used as templates to produce scaffolds with facile tunable porous structure, excellent cytocompatibility, and biodegradability. In this study, very stable high internal phase Pickering emulsions (HIPPE) with an oil content of 80% were successfully prepared by xylan hydrate nanocrystals (XNC). The HIPPE can exist stably for more than 30 days, exhibiting a high viscosity. By adding cellulose nanofibers (CNF) and removing the oil phase, scaffolds with a tuned porous structure and enhanced cell culturing ability were successfully fabricated. In the HIPPE templated scaffolds with XNC/CNF, XNC plays a major role in stabilizing the emulsions, while CNF improves the mechanical properties of the scaffolds, both of which are vital to the successful fabrication of the scaffolds. Compared with non-HIPPE templated scaffolds, the HIPPE templated scaffold had a higher porosity and a higher median pore size. The HIPPE templated scaffold was able to maintain 80% cell activity and showed an excellent cytocompatibility. The HIPPE templated scaffolds consisting of XNC and CNF demonstrate great potential in 3D cell culturing for medical purpose.

Facile synthesis and biomimetic amine-functionalization of chitosan foam for CO2 capture

A high-performance biomass-based adsorption materials could be the promising trend for CO2 capture and storage technology. However, the direct application of biomass-based porous materials as a CO2 adsorbent with enhanced performance is an emerging issue. Herein, a facile synthesis and a biomimetic strategy were combined to prepare amine-functionalized chitosan foam for CO2 capture, and then a porous biomass is achieved for the application on the environment protection field. Firstly, the chitosan foam was synthesized by the emulsion-templating method at room temperature. Depended on stabilizing n-octane in the chitosan hydrogel with Span 80, a tunable three-dimensional network porous structure was obtained. Subsequently, co-deposition with dopamine (DA) and polyethyleneimine (PEI) was applied to load abundant amine content on the surface of chitosan foam and thereby improving CO2 adsorption capacity. Finally, the as-prepared amine-functionalized chitosan foam exhibited the impressive adsorption capacity of 3.59 mmol/g at 333 K and atmospheric pressure, and the better adsorption selectivity and stability. The results extend the preparation approach of biomass porous materials, and also its application in CO2 adsorption technology.

Fluorescent Porous Materials Based on Aggregation-induced Emission for Biomedical Applications.

Fluorescent porous materials based on aggregation-induced emission (AIE) are growing into a sparkling frontier in biomedical applications. Exploring those materials represents a win-win integration and has recently progressed at a rapid pace, mainly benefiting from intrinsic advantages including tunable pore size and structure, strong guest molecule encapsulation ability, superior biocompatibility, and photophysical outcomes. With the great significance and rapid progress in this area, this review provides an integrated picture on AIE luminogen-based porous materials. It encompasses inorganic, organic, and inorganic-organic porous materials, exploring fundamental concepts and the relationship between AIE performance and material design and highlighting significant breakthroughs and the latest trends in biomedical applications. In addition, some critical challenges and future perspectives in the development of AIE luminogen-based porous materials are also discussed.

Zinc cobaltite embedded in binary metal-organic frameworks using a direct binder-free electrode fabrication approach for efficient energy storage devices and monosodium glutamate detection

There is an imperative need to develop high performance electrode for advance energy storage devices. This work represents the successful synthesis of zinc cobaltite (ZnCo2O4), nickel cobalt metal organic framework, and their composite (ZnCo2O4@NiCo-MOF). The materials are synthesized by using both hydrothermal and sonication techniques. The ZnCo2O4 offers eco-friendly and diffusion regulated properties, while NiCo-MOF provides large specific surface area and tunable pore structure. The ZnCo2O4@NiCo-MOF provide superior electrochemical performance compared to ZnCo2O4 and NiCo-MOF in a three electrode setup. The ZnCo2O4@NiCo-MOF provides a specific capacity of 984 C/g at 1.5 A/g. The ZnCo2O4@NiCo-MOF is also utilized in two electrode setup with activated carbon. The ZnCo2O4@NiCo-MOF//AC device demonstrates the energy density of 92.4 Wh/kg and a power density of 930 W/kg. Additionally, the real time application of ZnCo2O4@NiCo-MOF electrode is also tested in the detection of monosodium glutamate in food. This study highlights the importance of ZnCo2O4@NiCo-MOF electrode materials for future storage and detection devices.

From Nanozymes to Multi-Purpose Nanomaterials: The Potential of Metal-Organic Frameworks for Proteomics Applications.

Metal-organic frameworks (MOFs) have the potential to revolutionize the biotechnological and medical landscapes due to their easily tunable crystalline porous structure. Herein, the study presents MOFs' potential impact on proteomics, unveiling the diverse roles MOFs can play to boost it. Although MOFs are excellent catalysts in other scientific disciplines, their role as catalysts in proteomics applications remains largely underexplored, despite protein cleavage being of crucial importance in proteomics protocols. Additionally, the study discusses evolving MOF materials that are tailored for proteomics, showcasing their structural diversity and functional advantages compared to other types of materials used for similar applications. MOFs can be developed to seamlessly integrate into proteomics workflows due to their tunable features, contributing to protein separation, peptide enrichment, and ionization for mass spectrometry. This review is meant as a guide to help bridge the gap between material scientists, engineers, and MOF chemists and on the other side researchers in biology or bioinformatics working in proteomics.

Engineering modulation of cellulose-induced metal–organic frameworks assembly behavior for advanced adsorption and separation

The exploration of methods to remove harmful pollutants has become inevitable due to the increasing number of industries and the intensification and acceleration of environmental pollution. Therefore, the development of effective adsorption and separation process technologies is essential to ensure environmental remediation. Metal-organic framework (MOF) has attracted great attention in adsorption and separation area due to its large porosity, large specific surface area, tunable pore structure, and high chemical and thermal stability. However, the powder state of MOF results in weak flexibility, manufacturability, and recyclability, severely limiting its application. In this case, the synthesis of MOF composites by in-situ or ex-situ growth with abundant and sustainable cellulose family materials is an effective strategy for stabilizing these MOF species, modulating the assembly behavior of MOF, and expanding the forms of MOF application. Particularly, exciting research activities have emerged ranging from fabrication strategies for cellulose/MOF composites to adsorption and separation applications. In this review, the recent advances in cellulose/MOF composites regarding assembly methods, processing strategies, and adsorption and separation areas are comprehensively summarized. Meanwhile, focusing on the design concept of using cellulose to regulate the assembly behavior of MOF to construct macrostructures, the property characteristics and design principles of cellulose/MOF composites are deeply analyzed with examples. Moreover, the crucial challenges and future perspectives are also meticulously analyzed and discussed. We sincerely hope this review can further promote the research enthusiasm for cellulose/MOF composites in adsorption and separation applications and provide useful references for the design and application strategies of cellulose/MOF.

Cellulose nanofiber powered interface engineering strategy to manufacture mechanically stable, moldable, recyclable, and biodegradable cellulose foam

In this work, an ingenious and energy-efficient interface engineering strategy is developed to manufacture pulp cellulose foam via incorporating cellulose nanofiber/alkyl ketene dimer (CNF/AKD) Pickering emulsions. In this strategy, CNF/AKD emulsion can uniformly anchor onto pulp microfiber surface, not only achieving interfacial exoskeleton reinforcement, but also enabling low energy surface, which facilitates the direct and large-scale production of lightweight pulp/CNF/AKD (PCA) foam by oven drying without requiring any harmful crosslinking chemistries. By simply regulating the mass fractions of CNF and AKD in emulsion, the prepared PCA foams can achieve excellent and tunable 3D porous structure, mechanical performance, water resistance and wet stability. The dry compressive modulus and wet compressive modulus underwater of PCA foams with low density of 0.09 g/cm3 can reach 0.67 and 0.57 MPa, respectively. Even 1 week in water, the compressive modulus still retains 76.2 % of initial modulus. Notably, the proposed interface engineering strategy provides remarkable formability, moldability and structural designability, enabling cellulose foam to be customized into complex and delicate 3D macroscopic structures for different scenarios. Furthermore, the PCA foam displays economically feasible closed-loop recyclability by easy hot-water disintegration and natural biodegradability in soil. Therefore, this work proves a cost-effective and viable interface engineering strategy for scalable production of lightweight, mechanically stable, recyclable, biodegradable cellulose foams with high environmental benefits and low petrochemical consumption.

High-Performance Carbon Molecular Sieve Membranes Derived from a PPA-Cross-linked Polyimide Precursor for Gas Separation.

Carbon molecular sieve (CMS) membranes have emerged as attractive gas membranes due to their tunable pore structure and consequently high gas separation performances. In particular, polyimides (PIs) have been considered as promising CMS precursors because of their tunable structure, superior gas separation performance, and excellent thermal and mechanical strength. In the present work, polyphosphoric acid (PPA) was employed as both cross-linker and porogen, it created pores within the PI polymeric matrix, while it also effectively acting as a cross-linker to regulate the ultramicropores of the CMS membranes, thus simultaneously improving both permeability and selectivity of the CMS membranes. By employing PI/PPA hybrid with PPA content of 5 wt % as a precursor, the obtained CMS membrane exhibited a CO2 and He permeability of 1378.3 Barrer and 1431.4 Barrer, respectively, which was an approximately 10-fold increase compared to the precursor membrane. Under optimized conditions, the CO2/CH4 and He/CH4 selectivity of the obtained CMS membrane reached 81.5 and 89.9, respectively, which was 278% and 307% higher than that of the pristine PI membrane. In addition, the membrane exhibited good long-term stability during a one-week continuous test. This study clearly denoted PPA can be used for precisely tailoring the ultramicroporosity of CMS membranes.

Superhydrophobic cement with hierarchically tunable pore structure by additive manufacturing towards super sound absorption

Noise pollution as a form of environmental problem can have significant negative impacts on human health and the economy. To address this issue, a variety of noise-reduction construction materials have been developed. However, most present noise reduction materials suffer from a narrow absorbing band due to the simple pore structure which restricts their ability to absorb sound energy across a wide frequency range. Here, we demonstrate a hydrogel templating method and create hierarchically structured cement-based materials with tunable pore sizes by means of additive manufacturing. The introduction of this hierarchically tunable structure with micro-nano pores generated by cement hydration contributes to the formation of multi-scale pores (micro-, meso- and macropores), which achieves a sound absorption coefficient of 0.89 at 1000 Hz and ensures broadband acoustic absorption performance (noise reduction coefficient of 0.54, around 50 % improvement compared to traditional construction sound absorption materials). Meantime, this lightweight material has good compressive strength (1.31 MPa) and superhydrophobicity (water contact angle of 152.5°), together with thermal conductivity (0.088 W m−1 K−1) and excellent fire resistance. This study provides a new approach for designing cement-based materials with super sound absorption.

Boosting HER performance of ZIF-67 via optimizing synthesis parameters in alkaline medium

Electrochemical water splitting offers a promising route to sustainable hydrogen production. Metal-Organic Frameworks (MOFs) have emerged as potential electrocatalysts due to their tunable structure and composition. We investigated the electrocatalytic activity of ZIF-67 for the hydrogen evolution reaction (HER) in alkaline media. Synthesis parameters, including temperature, reaction time, acidity, molar ratio of 2-methylimidazole (2-MIM) to cobalt source, cobalt source type, addition method of 2-MIM, and solvent type, were systematically varied to optimize the electrocatalytic properties of ZIF-67. The synthesized ZIF-67 electrocatalysts were characterized using BET, FESEM, EDS, TEM, XRD, FTIR, and UV–vis spectroscopy. The electrocatalytic properties were evaluated by cyclic voltammetry (CV), linear sweep voltammetry (LSV), electrochemical impedance spectroscopy (EIS), and chronoamperometry methods. The optimized ZIF-67 electrocatalyst exhibited remarkable performance, with a low overpotential of 171 mV, a small Tafel slope of 82 mV.dec−1, a low charge transfer resistance of 97 Ω, a high double-layer capacitance of 13.5 mF cm−2, and high stability for 15 h at the current density of 10 mA cm−2. The enhanced electrocatalytic activity of the optimized ZIF-67 was attributed to its high surface area, tunable pore structure, and the presence of active cobalt sites.

Advances in sustainable nano-biochar: precursors, synthesis methods and applications.

Nano-biochar, characterized by its environmentally friendly nature and unique nanostructure, offers a promising avenue for sustainable carbon materials. With its small particle size, large specific surface area, abundant functional groups and tunable pore structure, nano-biochar stands out due to its distinct physical and chemical properties compared to conventional biochar. This paper aims to provide an in-depth exploration of nano-biochar, covering its sources, transformation mechanisms, properties, applications, and areas requiring further research. The discussion begins with an overview of biomass sources for nano-biochar production and the conversion processes involved. Subsequently, primary synthesis methods and strategies for functionalization enhancement are examined. Furthermore, the applications of nano-biochar in catalysis, energy storage, and pollutant adsorption and degradation are explored and enhanced in various fields.

Organosilica with tunable pore structure and antibacterial activity for intelligent humidity control

The spontaneous sorption and release of moisture by sorbents is proposed to be an energy-saving strategy for air humidity control. However, rational design of sorbents with humidity control ability and wide applicability still faces challenges. This study demonstrates quaternary ammonium-functionalized organosilica capable of controlling humidity intelligently and tuning humidity range as required. The prepared organosilica exhibited step-shaped water sorption isotherm due to its highly ordered pore structure, which was capable of precisely maintaining humidity within a narrow range. Importantly, the step position could be broadly tuned by easily changing the pore size during synthesis. Series organosilica with different pore sizes could realize humidity maintenance in 20%-40%, 40%-60% and 55%-80%, respectively, making it suitable for diverse humidity control applications. Grand Canonical Monte Carlo simulations elucidated the underlying mechanism of different water sorption behaviors in different pore structures. Quaternary ammonium groups act as the initial nucleation sites for water vapor, followed by distinct water condensation mechanisms in micropores (pore filling) and mesopores (capillary condensation), respectively. Moreover, organosilica exhibits efficient antibacterial activity and self-cleaning capability due to the function of quaternary ammonium groups. The organosilica with tunable pore structure and antibacterial activity provides a new model for intelligent and low-energy humidity control.

Investigating solvent effects on synthesizing novel cobalt hydroxide and fluoride complex from Co(BF4)2 as active materials of the battery supercapacitor hybrid

Metal-organic framework (MOF) derivatives with tunable pore structure and improved conductivity are intensively designed as electroactive materials. Incorporating structure directing agents (SDA) is beneficial for designing MOF derivatives with excellent electrochemical performances. Ammonium fluoroborate has been reported as an effective SDA, coupled with cobalt salt and 2-methylimidazole, to synthesize zeolitic imidazolate framework-67 (ZIF-67) derivatives for charge storage. However, the synthetic environment for growing cobalt-based active materials is relatively complex. In this study, cobalt tetrafluoroborate (Co(BF4)2) is proposed as a novel cobalt precursor, supplementing cobalt ions and acting as the SDA in a single chemical, to synthesize the cobalt-based electroactive material of energy storage electrodes. Interactions between solvent molecules and solutes play significant roles on the morphology, composition, and electrochemical performance of active materials. Deionized water, methanol and ethanol are used as precursor solvents to understand their effects on material and electrochemical properties. The optimal electrode presents a specific capacitance of 608.3 F/g at 20 mV/s, attributed to the highest electrochemical surface area and evident compositions of cobalt fluoride and hydroxide. A battery supercapacitor hybrid achieves the maximum energy density of 45 Wh/kg at 429 W/kg. The CF retention of 100% and Coulombic efficiency of 99% are achieved after 10,000 cycles.

Polyphenol-Derived Carbonaceous Frameworks with Multiscale Porosity for High-Power Electrochemical Applications.

With the escalating global demand for electric vehicles and sustainable energy solutions, increasing focus is placed on developing electrochemical systems that offer fast charging and high-power output, primarily governed by mass transport. Accordingly, porous carbons have emerged as highly promising electrochemically active or supporting materials due to expansive surface areas, tunable pore structures, and superior electrical conductivity, accelerating surface reaction. Yet, while substantial research has been devoted to crafting various porous carbons to increase specific surface areas, the optimal utilization of the surfaces remains underexplored. This review emphasizes the critical role of the fluid dynamics within multiscale porous carbonaceous electrodes, leading to substantially enhanced pore utilization in electrochemical systems. It elaborates on strategies of using sacrificial templates for incorporating meso/macropores into microporous carbon matrix, while exploiting the unique properties of polyphenol moieties such as sustainable carbons derived from biomass, inherent adhesive/cohesive interactions with template materials, and facile complexation capabilities with diverse materials, thereby enabling adaptive structural modulations. Furthermore, it explores how multiscale pore configurations influence pore-utilization efficiency, demonstrating advantages of incorporating multiscale pores. Finally, synergistic impact on the high-power electrochemical systems is examined, attributed to improved fluid-dynamic behavior within the carbonaceous frameworks, providing insights for advancing next-generation high-power electrochemical applications.