Hydrophobicity-Adjustable MOF Constructs Superhydrophobic MOF-rGO Aerogel for Efficient Oil-Water Separation

Green fabrication of highly flame-retardant, anti-ultraviolet radiation and superhydrophobiccellulose-based fabric by constructing dualtielement-containing NH2-MIL-53(Al)@Triethoxyoctylsilane nano coatings

The facile and eco-friendly fabrication of a fabric with remarkable flame retardancy, anti-ultraviolet (UV), and superhydrophobic properties is of significant interest for multitask requirements. In this regard, herein, a nonfluorine, facile, and green method is reported for in situ synthesis of metal-organic frame (NH2-MIL-53(Al)) on hemp fabric (HF) for the preparation of multifunctional textiles. A homogeneous and compact coating of NH2-MIL-53(Al) crystals was deposited on HF, followed by modification with triethoxyoctylsilane (TEOS) to manufacture superhydrophobic NH2-MIL-53(Al)@hemp fabric (SM(Al)HF-9), significantly enhancing its water stability. The SM(Al)HF-9 exhibited superior superhydrophobicity properties, with a water contact angle (WCA) up to 156°. Furthermore, the surface of SM(Al)HF-9 cannot be adhered by dye solution and powder, indicating its good self-cleaning and anti-fouling abilities. The SM(Al)HF-9, characterized by a porous structure, effectively separates tetrachloromethane and n-hexane from water mixtures with a separation efficiency exceeding 97 %. The SM(Al)HF-9 has excellent UV-blocking properties, and the UV protection factor is as high as 105.44. Encouragingly, the SM(Al)HF-9 exhibited outstanding flame retardancy, as demonstrated by its self-extinguishing capability and a substantially improved limiting oxygen index (LOI) of 32.4 %. In comparison to raw HF, the peak heat release rate (PHRR) and total heat rate (THR) of the modified HF are reduced by 76.15 % and 54.32 %, respectively. Meanwhile, the NH2-MIL-53(Al) has a significant advantage over other MOFs (e.g., ZIF-67, Ce-MOF, Ag-MOF, Fe-MOF and MIL-53(Al)) in improving the flame retardancy of HF. The highly efficient flame-retardant, anti-UV, and superhydrophobic fabric is promising in home and public decoration, and fire protection fields.

Environmental applications of metal-organic framework-based three-dimensional macrostructures: a review

Metal-organic frameworks (MOFs) hold considerable promise for environmental remediation owing to their exceptional performance and distinctive structure. Nonetheless, the practical implementation of MOFs encounters persistent technical hurdles, notably susceptibility to loss, challenging recovery, and potential environmental toxicity arising from the fragility, insolubility, and poor processability of MOFs. MOF-based three-dimensional macrostructures (3DMs) inherit the advantageous attributes of the original MOFs, such as ultra-high specific surface area, tunable pore size, and customizable structure, while also incorporating the intriguing characteristics of bulk materials, including hierarchical structure, facile manipulation, and structural flexibility. Consequently, they exhibit rapid mass transfer and exceptional practicality, offering extensive potential applications in environmental remediation. This review presents a comprehensive overview of recent advancements in utilizing MOF-based 3DMs for environmental remediation, encompassing their fascinating characteristics, preparation strategies, and characterization methods, and highlighting their exceptional performance in pollutant adsorption, catalysis, and detection. Furthermore, existing challenges and prospects are presented to advance the utilization of MOF-based materials across various domains, particularly in environmental remediation.

Recent advances in the synthesis and application of graphene aerogel and silica aerogel for environment and energy storage: A review

Aerogel materials have gained considerable attention in recent years due to their promising applications in environmental and energy storage fields, owing to their exceptional properties, including high porosity, ultra-low thermal conductivity, low density, and high specific surface area. This review begins by examining novel synthesis techniques, including sol-gel processing, chemical crosslinking, and templating, that enhance both the microstructural and functional properties of aerogels. Next, we explore the applications of graphene and silica aerogels in environmental and energy conservation technologies. Graphene aerogels, in particular, demonstrate significant potential in water purification by effectively removing antibiotics, offering a new approach to water treatment. The combination of silica aerogels with phase change materials, along with their use in supercapacitors, demonstrates their potential for energy conservation. Additionally, we discuss the synergistic effects of silica and graphene aerogels, which further broaden their applications. Finally, the paper concludes by summarizing the potential of graphene and silica aerogels as functional materials for environmental applications and outlining the challenges and future directions for their development and industrial use.

Metal-Organic Frameworks (MOFs) and Their Composites for Oil/Water Separation

Contamination of water by oil-based pollutants is a major environmental problem because of its harmful impact on human life, marine life, and the environment. As a result, a wide range of materials are being investigated for the effective separation of oil from water. Among these materials, metal-organic frameworks (MOFs) and their composites have emerged as excellent candidates due to their ultraporous structures with high surface areas that can be engineered to achieve high selectivity for one of the phases in an oil/water mixture for efficient water filtration. However, the often nanocrystalline/microcrystalline form of MOFs combined with challenges of processability and poor stability in water has largely limited their use in industrial and environmental applications. Hence, considerable efforts have recently been made to improve the performance and stability of MOFs by introducing hydrophobic functional groups into the organic linkers and fabricating polymer-MOF composites to increase their stability and recyclability. In addition, the use of biobased or biodegradable MOF composites can be particularly useful for applications in natural environments. This Review presents recent advances in the field of hydrophobic MOFs and MOF-based composites studied for the separation of oil from oil/water mixtures, with an account of future challenges in this area.

Metal-Organic Framework and Covalent-Organic Framework-Based Aerogels: Synthesis, Functionality, and Applications

Metal-organic frameworks (MOFs) and covalent-organic frameworks (COFs)-based aerogels are garnering significant attention owing to their unique chemical and structural properties. These materials harmoniously combine the advantages of MOFs and COFs-such as high surface area, customizable porosity, and varied chemical functionality-with the lightweight and structured porosity characteristic of aerogels. This combination opens up new avenues for advanced applications in fields where material efficiency and enhanced functionality are critical. This review provides a comparative overview of the synthetic strategies utilized to produce pristine MOF/COF aerogels as well as MOF/COF-based hybrid aerogels, which are functionalized with molecular precursors and nanoscale materials. The versatility of these aerogels positions them as promising candidates for addressing complex challenges in environmental remediation, energy storage and conversion, sustainable water-energy technologies, and chemical separations. Furthermore, this study discusses the current challenges and future prospects related to the synthesis techniques and applications of MOF/COF aerogels.

Bioaerogels from biomass waste: An alternative sustainable approach for wastewater treatment

The generation of municipal solid waste is projected to increase from 2.1 billion tonnes in 2023 to 3.8 billion tonnes by 2050. In 2020, the direct global cost of managing this waste was approximately USD 252 billion. When considering additional hidden costs-such as those arising from pollution, adverse health effects, and climate change due to inadequate waste disposal-the total cost escalates to USD 361 billion. Without significant improvements in waste management practices, this figure could nearly double by 2050, reaching an estimated USD 640.3 billion annually. Among municipal solid waste, biowaste accounts for roughly 44 % of the global municipal solid waste, translating to about 840 million tonnes annually. They are widely accessible and economical, offering a cost-effective alternative to traditional treatment materials. Transforming biomass waste into carbon-based materials (e.g., bioaerogels) is a sustainable practice that reduces waste and repurposes it for environmental remediation. This approach not only decreases the volume of waste directed to landfills and mitigates harmful greenhouse gas emissions from decomposition but also aligns with the principles of a circular economy. Furthermore, it supports sustainable development goals by addressing issues such as water scarcity and pollution while promoting waste valorization and resource efficiency. The unique properties of bioaerogels-including their porosity, multi-layered structure, and chemical adaptability-make them highly effective for the remediation of different water pollutants from aquatic bodies. This review article comprehensively delves into multifaceted wastewater remediation strategies -based bioaerogels such as coagulation and flocculation, advanced oxidation processes, membrane filtration, catalytic processes, water disinfection, Oil-water separation, biodegradation, and adsorption. Additionally, it examines different mechanisms of interaction such as surface adsorption, electrostatic interaction, van der Waals forces, ion exchange, surface precipitation, complexation, pore-filling, hydrophobic interactions, and π-π stacking. Moreover, it conducts an integrated techno-economic evaluation to assess their feasibility in wastewater treatment. By valorizing biomass waste, a closed-loop system can be established, where waste is transformed into valuable bioaerogels. This approach not only addresses challenges related to effluent pollution but also generates economic, environmental, and social benefits. Ultimately, the review underscores the transformative potential of bioaerogels in wastewater treatment, emphasizing their crucial role in supporting long-term environmental goals and advancing the principles of resource circularity.

Recent Progress in MOF-Aerogel Fabrication and Applications

Recent advancements in metal-organic frameworks (MOFs) underscore their significant potential in chemical and materials research, owing to their remarkable properties and diverse structures. Despite challenges like intrinsic brittleness, powdered crystalline nature, and limited stability impeding direct applications, MOF-based aerogels have shown superior performance in various areas, particularly in water treatment and contaminant removal. This review highlights the latest progress in MOF-based aerogels, with a focus on hybrid systems incorporating materials like graphene, carbon nanotube, silica, and cellulose in MOF aerogels, which enhance their functional properties. The manifold advantages of MOF-based aerogels in energy storage, adsorption, and catalysis are discussed, with an emphasizing on their improved stability, processability, and ease of handling. This review aims to unlock the potential of MOF-based aerogels and their real-world applications. Aerogels are expected to reshape the technological landscape of MOFs through enhanced stability, adaptability, and efficiency.

Bifunctional folic acid targeted biopolymer Ag@NMOF nanocomposite [{Zn2 (1,4-bdc) 2 (DABCO)} n] as a novel theranostic agent for molecular imaging of colon cancer by SERS

Without a doubt, cancer and its negative impact on human health have created many hurdles for people across the world since conventional approaches have not offered a reliable ability in the eradication of cancer. As a result, finding novel approaches, like using bimodal nanoparticles as a potential nanocarrier in molecular imaging and cancer therapy, is remarkably required these days. In the present study, ex-situ (Ge) and in-situ (Gi) green synthesized silver (Ag) nanoparticles entrapped in metal-organic framework nanocomposites (NMOF) coated with folic acid (FA) targeted chitosan (CS) was successfully developed as a novel bifunctional nanocarrier for detection and treatment of colon cancer cells. Then nanocarriers, such as NMOF-CS-FA, Ge-Ag@NMOF-CS-FA, Gi-Ag@NMOF-CS-FA, and C-Ag@NMOF-CS-FA, were characterized via FT-IR, DLS, SERS, TEM, and SEM and results have potentially confirmed the quality and quantity of synthesized nanocomposites. The hydrodynamic diameters of NMOF-CS, Ge-Ag@NMOF-CS, Gi-Ag@NMOF-CS, and C-Ag@NMOF-CS specimens were measured at around 99.7 ± 10 nm, 110 ± 10 nm, 118 ± 10 nm, 115 ± 10 nm, respectively. Also, the PDI values less than 0.2 confirm the reliable distribution of these nanocomposites. Afterward, the cell viability assay was conducted on HCT116 and HGF cell lines for evaluating biocompatibility and targeting efficiency of nanocomposites; FA functionalized nanocomposites have intensively indicated better performance in cancer cells targeting and their inhibition, and IC50 was attained for 10 ng/mL of Ge-Ag@NMOF-CS-FA while non-targeted nanocarriers did not have toxicity more than 20 % on HCT116 colon cancer cells. Moreover, according to the results, the cell viability of HGF normal cells was at least 85 % after being exposed to different concentrations of nanocomposites for 24 h. This indicates that the synthesized nanocomposites do not have significant toxic effects on normal cells. The results indicate that this novel nanocomposite has the potential to effectively deliver drugs to cancer cells.

Thermodynamically and Kinetically Enhanced Benzene Vapor Sensor Based on the Cu-TCPP-Cu MOF with Extremely Low Limit of Detection

As a carcinogenic and highly neurotoxic hazardous gas, benzene vapor is particularly difficult to be distinguished in BTEX (benzene, toluene, ethylbenzene, xylene) atmosphere and be detected in low concentrations due to its chemical inertness. Herein, we develop a depth-related pore structure in Cu-TCPP-Cu to thermodynamically and kinetically enhance the adsorption of benzene vapor and realize the detection of ultralow-temperature benzene gas. We find that the in-plane π electronic nature and proper pore sizes in Cu-TCPP-Cu can selectively induce the adsorption and diffusion of BTEX. Interestingly, the theoretical calculations (including density functional theory (DFT) and grand canonical Monte Carlo (GCMC) simulations) exhibit that benzene molecules are preferred to adsorb and array as a consecutive arrangement mode in the Cu-TCPP-Cu pore, while the TEX (toluene, ethylbenzene, xylene) dominate the jumping arrangement model. The differences in distribution behaviors can allow adsorption and diffusion of more benzene molecules within limited room. Furthermore, the optimal pore-depth range (60-65 nm) of Cu-TCPP-Cu allows more exposure of active sites and hinders the gas-blocking process. The optimized sensor exhibits ultrahigh sensitivity to benzene vapor (155 Hz/μg@1 ppm), fast response time (less than 10 s), extremely low limit of detection (65 ppb), and excellent selectivity (83%). Our research thus provides a fundamental understanding to design and optimize two-dimensional metal-organic framework (MOF)-based gas sensors.

Nanoarchitectonics Design Strategy of Metal-Organic Framework and Bio-Metal-Organic Framework Composites for Advanced Wastewater Treatment through Adsorption

Freshwater depletion is an alarm for finding an eco-friendly solution to treat wastewater for drinking and domestic applications. Though several methods like chlorination, filtration, and coagulation-sedimentation are conventionally employed for water treatment, these methods need to be improved as they are not environmentally friendly, rely on chemicals, and are ineffective for all kinds of pollutants. These problems can be addressed by employing an alternative solution that is effective for efficient water treatment and favors commercial aspects. Metal organic frameworks (MOFs), an emerging porous material, possess high stability, pore size tunability, greater surface area, and active sites. These MOFs can be tailored; thus, they can be customized according to the target pollutant. Hence, MOFs can be employed as adsorbents that effectively target different pollutants. Bio-MOFs are a kind of MOFs that are incorporated with biomolecules, which also possess properties of MOFs and are used as a nontoxic adsorbent. In this review, we elaborate on the interaction between MOFs and target pollutants, the role of linkers in the adsorption of contaminants, tailoring strategy that can be employed on MOFs and Bio-MOFs to target specific pollutants, and we also highlight the effect of environmental matrices on adsorption of pollutants by MOFs.

Ratiometric fluorescent and electrochemiluminescent dual modal assay for detection of 2,6-pyridinedicarboxylic acid as an anthrax biomarker

2,6-pyridinedicarboxylic acid (DPA) is an excellent biomarker of Bacillus anthracis (B. anthracis). The sensitive detection of DPA, especially through visual point-of-care testing, was significant for accurate and rapid diagnosis of anthrax to timely prevent anthrax disease or biological terrorist attack. Herein, a ratiometric fluorescent (R-FL) and electrochemiluminescent (ECL) dual-mode detection platform with a lanthanide ion-based metal-organic framework (Ln-MOF, i.e., M/Y-X: M = Eu, Y = Tb, and X = 4,4',4″-s-triazine-1,3,5-triyltri-m-aminobenzoic acid) was developed. Eu/Tb-TATAB nanoparticles were constructed to identify DPA. The R-FL detection platform quantitatively detected DPA by monitoring the I545/I617 ratio of the characteristic fluorescence peak intensities of Tb3+ ions and Eu3+ ions. The ECL sensing platform successfully quantified DPA by exploiting the burst effect of DPA on the ECL signal. The above methods had highly sensitive and rapid detection of DPA in water and serum samples. The results showed that this dual-mode detection platform may be projected to be a powerful instrument for preventing related biological warfare and bio-terrorism.

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.

Metal-Organic Framework Gels for Adsorption and Catalytic Detoxification of Chemical Warfare Agents: A Review

Chemical warfare agents (CWAs) have brought great threats to human life and social stability, and it is critical to investigate protective materials. MOF (metal-organic framework) gels are a class with an extended MOF architecture that are mainly formed using metal-ligand coordination as an effective force to drive gelation, and these gels combine the unique characteristics of MOFs and organic gel materials. They have the advantages of a hierarchically porous structure, a large specific surface area, machinable block structures and rich metal active sites, which inherently meet the requirements for adsorption and catalytic detoxification of CWAs. A series of advances have been made in the adsorption and catalytic detoxification of MOF gels as chemical warfare agents; however, overall, they are still in their infancy. This review briefly introduces the latest advances in MOF gels, including pure MOF gels and MOF composite gels, and discusses the application of MOF gels in the adsorption and catalytic detoxification of CWAs. Meanwhile, the influence of microstructures (pore structures, metal active site, etc.) on the detoxification performance of protective materials is also discussed, which is of great significance in the exploration of high-efficiency protective materials. Finally, the review looks ahead to next priorities. Hopefully, this review can inspire more and more researchers to enrich the performance of MOF gels for applications in chemical protection and other purification and detoxification processes.

A biomimetic design for efficient petrochemical spill disposal: CoFe-PBA modified superhydrophobic melamine sponge with mechanical/chemical durability and low fire risk

Due to frequent petrochemical spills, environmental pollution and the threat of secondary marine fires have arisen, necessitating an urgent need for petrochemical spill treatment strategies with high-performance oil-water separation capabilities. To address the challenges of poor durability, instability in hydrophobic conditions, and difficulty in absorbing high-viscosity crude oil associated with hydrophobic absorbent materials, the authors of this study took inspiration from the unique micro and nanostructures of springtails' water-repellent skin. We engineered a superhydrophobic melamine sponge using interfacial assembly techniques designated as Si@PBA@PDA@MS. This material demonstrated improved mechanical and chemical durability, enhanced photothermal performance, and reduced fire risk. The metal-organic framework (MOF)-derived cobalt-iron Prussian blue analog (CoFe-PBA) was firmly anchored to the sponge framework by the chelation of cobalt ions using polydopamine (PDA). The results demonstrated that Si@PBA@PDA@MS demonstrated excellent superhydrophobicity (WCA=163.5°) and oil absorption capacity (53.4-97.5 g/g), maintaining high durability even after 20 cycles of absorption-squeezing. Additionally, it could still exhibit excellent mechanical properties, hydrophobic stability, and absorption performance across a wide temperature range (0-100 °C), pH range (1-14), and high compression strength (ε = 80%), with excellent mechanical/chemical durability. Furthermore, Si@PBA@PDA@MS demonstrated remarkable photothermal performance and low fire risk, offering efficient, safe, and sustainable practical value for effective petrochemical spill treatment.

Tuning Electrical and Mechanical Properties of Metal-Organic Frameworks by Metal Substitution

Metal-organic frameworks (MOFs), synthesized by the self-assembly of organic ligands and metal centers, are structurally designable materials. In the current study, first-principles calculation based on density functional theory (DFT) was performed to investigate the intrinsic mechanical and electrical properties and mechanical-electrical coupling behavior of MOF-5. To improve the conductivity of MOF-5, homologous elements of Cu, Ag, and Au were adopted to replace the Zn atom in MOF-5, reducing the band gap and improving its electrical performance. Cu-MOF-5 and Au-MOF-5, with stable structures, exhibit better conductivity. The intrinsic mechanical properties such as independent elastic constants of MOF-5 and M-MOF-5 (M = Cu, Ag, Au) were obtained. MOF-5 and Cu-MOF-5 were experimentally synthesized to demonstrate the reduction in the band gap after metal substitution. The study of the strain effect of MOF-5 and Cu-MOF-5 proves that strain engineering is an effective method to regulate the band gap and this modulation is repeatable. This study clarifies the tunability of the band gap of MOF-5 with metal substituents and provides an efficient strategy for the development of new types of MOFs with desired physical properties using the combination of theoretical prediction and experimental synthesis and validation.

Microporous Organic Network: Superhydrophobic Coating to Protect Metal-Organic Frameworks from Hydrolytic Degradation

Despite the rapid development of versatile metal-organic frameworks (MOFs), the synthesis of water-stable MOFs remains challenging, which significantly limits their practical applications. Herein, a novel engineering strategy was developed to prepare superhydrophobic MOFs by an in situ fluorinated microporous organic network (FMON) coating. Through controllable modification, the resulting MOF@FMON retained the porosity and crystallinity of the pristine MOFs. Owing to the superhydrophobicity of the FMON and the feasibility of MOF synthesis, the FMON coating could be in situ integrated with various water-sensitive MOFs to provide superhydrophobicity. The coating thickness and hydrophobicity of the MOF@FMON composites were easily regulated by changing the FMON monomer concentration. The MOF@FMON composites exhibited excellent oil/water separation and catalytic activities and enhanced durability in aqueous solutions. This study provides a general approach for the synthesis of superhydrophobic MOFs, expanding the application scope of MOFs.

Sodium Alginate-Based Carbon Aerogel-Supported ZIF-8-Derived Porous Carbon as an Effective Adsorbent for Methane Gas

Adsorption natural gas (ANG) is a technology in which natural gas is stored on the surface of porous materials at relatively low pressures, which are promising candidates for adsorption of natural gas. Adsorbent materials with a large surface area and porous structure plays a significant role in the ANG technology, which holds promise in increasing the storage density for natural gas while decreasing the operating pressure. Here, we demonstrate a facile synthetic method for rational construction of a sodium alginate (SA)/ZIF-8 composite carbon aerogel (AZSCA) by incorporating ZIF-8 particles into SA aerogel through a directional freeze-drying method followed by the carbonization process. The structure characterization shows that AZSCA has a hierarchical porous structure, in which the micropores originated from MOF while the mesopores are derived from the three-dimensional network of the aerogel. The experimental results show that AZSCA achieved high methane adsorption of 181 cm³·g^-1 at 65 bar and 298 K, along with higher isosteric heat of adsorption (Q_st) throughout the adsorption range. Thus, the combination of MOF powders with aerogel can find potential applications in other gas adsorption.

A comprehensive review of hydrophobic silica and composite aerogels: synthesis, properties and recent progress towards environmental remediation and biomedical applications

The hydrophobicity of silica and composite aerogels has enabled them to acquire applications in a variety of fields. With remarkable structural, morphological, and physiochemical properties such as high porosity, surface area, chemical stability, and selectivity, these materials have gained much attention of researchers worldwide. Moreover, the hydrophobic conduct has enabled these aerogels to adsorb substances, i.e., organic pollutants, without collapsing the pore and network structure. Hence, considering such phenomenal properties and great adsorption potential, exploiting these materials for environmental and biomedical applications is trending. The present study explores the most recent advances in synthetic approaches and resulting properties of hydrophobic silica and composite aerogels. It presents the various precursors and co-precursors used for hydrophobization and gives a comparative analysis of drying methods. Moreover, as a major focus, the work presents the recent progress where these materials have shown promising results for various environmental remediation and biomedical applications. Finally, the bottlenecks in synthesis and applicability along with future prospects are given in conclusions.

Rigid, eco-friendly and superhydrophobic SiO2-Polyvinyl alcohol composite sponge for durable oil remediation

Development of durable and eco-friendly adsorbents for oil remediation is in great demands. However, most of adsorbents were designed to pursue large capabilities while ignored their strength after adsorbing oil, which might cause secondary oil spilling during complex salvage process. Herein, an eco-friendly and superhydrophobic SiO₂-modified polyvinyl alcohol composite (H-SiO₂-G-PVA) sponge with extraordinary rigid structure after oil adsorption is designed for durable oil remediation. Through a two-step hydrolysis-condensation process including deposition of silica microparticles and introduction of hexadecyltrimethoxysilane (HDTMS), a superhydrophobic H-SiO₂-G-PVA sponge has been successfully constructed. The sponge presents stable superhydrophobicity in various complex environments，therefore it efficiently adsorbs oil from water (up to 6 g g^-1) and separate surfactant-stabilized water/oil emulsion with high efficiency (>99%). Noticeably, the H-SiO₂-G-PVA sponge maintains tough strength (3.5 MPa) after oil adsorption, which ideally overcomes secondary oil spilling problem and endows the sponge with excellent recycling performances (>20 cycles). Meanwhile, the excellent biocompatibility of the sponge (high cell viability of 91.85%) ensures the potential for practical applications. This rigid, eco-friendly oil-adsorbing sponge that achieves stable superhydrophobicity and recyclability, fulfills the application needs for durable oil remediation.

Durable 3D Porous Superhydrophobic Composites for Versatile Emulsion Separation in Multiple Environments

Polydopamine as a multifunctional biomimetic polymer with nonselective strong adhesion properties has become a hot research topic in recent years. However, there are a few reports on the durable and effective emulsion separation of polydopamine composites from other materials. Therefore, it is necessary to construct durable polydopamine composites to achieve selective adsorption of materials. In this work, polypyrrole (PPy)-PDA was obtained on sponges by an in situ polymerization reaction, followed by the attachment of SiO₂ nanoparticles to the surface by polydimethylsiloxane to achieve superhydrophobicity. As a result, previously unreported selective superhydrophobic adsorbents for PPy-PDA coatings were obtained. The prepared sponges have an excellent adsorption capacity for oils and organic solvents. Not only can the sponges absorb 19-39 g of organic solvents per gram but they can also absorb oil from oil-in-water emulsions. The chemical oxygen demand value of the emulsion can be reduced to 219 mg/L after separation. More importantly, the performance remains good in the cycle test, and due to the construction of a durable superhydrophobic sponge, it can still maintain its relatively good performance in artificial seawater, acid-base environments, and can achieve relatively stable emulsion separation. At the same time, the potential of the polymer material composited with PDA in lasting and stable emulsion separation was also verified.

Fabrication of Carbon Aerogels Derived from Metal-Organic Frameworks/Carbon Nanotubes/Cotton Composites as an Efficient Sorbent for Sustainable Oil–Water Separation

Due to the continuous occurrence of water pollution problems, practical separation methods for oil–water mixtures have attracted more and more attention. To date, different kinds of materials have been developed with good hydrophobic properties and strong separation ability. Carbon aerogels, as a promising ideal adsorbent for dealing with oil-spill accidents, have received extensive attention. In this work, zeolitic imidazolate frameworks (ZIFs), nanoparticles, and carbon nanotubes (CNTs) in the three-dimensional (3D) interconnected network structure of cotton balls (CBs) were successfully prepared by a simple and scalable process. The as-prepared carbonized CBs with carbonized ZIF-8 and CNTs (CZIF-8/CNTs/CCBs) were characterized. The oil–water separation performance of the composite was also measured. The results show that the ZIF-8 clusters intercalated with abundant CNTs are fully loaded into the porous structure of the CBs after the in situ synthesis process. Additionally, ZIF-8/CNTs/CBs was carbonized in nitrogen, leading to the formation of CZIF-8/CNTs/CCBs. The prepared material possesses excellent hydrophobicity with a water contact angle of 152.7°, showing good absorption capacities Q1 in the range of 48 to 84 times its original weight for oil and organic liquids. In addition, CZIF-8/CNTs/CCBs exhibits good recyclability in the absorption–distillation test. In summary, this study proposes a novel and simple method for the preparation of a superhydrophobic material that could have wide application in the separation of oil–water mixtures.

Advanced MOFs@aerogel composites: Construction and application towards environmental remediation

Environmental pollution has drawn forth advanced materials and progressive techniques concentrating on sustainable development. Metal-organic frameworks (MOFs) have aroused vast interest resulting from their excellent property in structure and function. Conversely, powdery MOFs in highly crystalline follow with fragility, poor processability and recoverability. Aerogels distinguished by the unique three-dimensional (3D) interconnected pore structures with high porosity and accessible surface area are promising carriers for MOFs. Given these, combining MOFs with aerogels at molecule level to obtain advanced composites is excepted to further enhance their performance with higher practicability. Herein, we focus on the latest studies on the MOFs@aerogel composites. The construction of MOFs@aerogel with different synthetic routes and drying methods are discussed. To explore the connection between structure and performance, pore structure engineering and quantitation of MOFs content are outlined. Furthermore, various types of MOFs@aerogel composites and their carbonized derivatives are reviewed, as well as the applications of MOFs@aerogel for environmental remediation referring to water purification and air clearing. More importantly, outlooks towards these emerging advanced composites have been presented from the perspective of practical application and future development.

Robust and Multifunctional 3D Graphene-Based Aerogels Reinforced by Hydroxyapatite Nanowires for Highly Efficient Organic Solvent Adsorption and Fluoride Removal

In view of the serious perniciousness and complex diversity of actual wastewater systems, exploiting a robust and multifunctional adsorbent material featuring high sorption efficiency, broad-spectrum applicability, and excellent recyclability in treating multifarious pollutants in water (such as oils and fluoride ions) is highly required; however, it is still a daunting goal to pursue to date. In this work, novel mechanically robust and exceptional graphene oxide/hydroxyapatite nanowire (GO/HAPNW) aerogels (RGHAs/polydopamine (PDA)@RGHAs) with adjustable surface wettability were developed through a facile sol-gel self-assembly technology and subsequently optional bioinspired hydrophilic modification. Thanks to the reinforcing effect of HAPNWs with higher aspect ratio, a remarkably improved mechanical robustness (including superior compressibility and superelasticity) was acquired for the resulting aerogels. Based on the cooperative effect of the favorable selective wetting properties (i.e., hydrophobic/oleophilic for RGHAs) and the excellent mechanic stability, the aerogels displayed an outstanding sorption performance for diverse oils/organic solvents accompanied with a prominent recyclability. Specifically, a fairly high adsorption capacity of as high as 191 times of its own mass (for pump oil) was achieved based on a fast adsorption kinetic process. More importantly, superamphiphilic three-dimensional (3D) PDA@RGHAs revealed an extraordinary removal capability for water-soluble fluoride ions, exhibiting a superior equilibrium adsorption capacity (q_e, 9.93 mg/g), which is distinctly superior to those of low-dimensional fluorine adsorbent materials recently reported. Accordingly, the as-prepared 3D aerogels combining both superior oil/organic solvent adsorption and excellent defluorination capability reveal a competitive application prospect toward effective intricate oily wastewater purification.

Mechanically robust Janus nanofibrous membrane with asymmetric wettability for high efficiency emulsion separation

Water pollution caused by oil leakage or oily sewage has seriously threatened the ecological environment and human health. It remains a tough task for scientists to develop versatile materials to purify different kinds of oily wastewater. In this study, we propose a facile "carbon nanotubes (CNTs) decoration and nanofibrous membrane integration" method to prepare a mechanical robust Janus membrane (JM) composed of a superhydrophilic nanofiber composite layer and a hydrophobic nanofiber composite layer. The asymmetric wettability can be controlled by tuning the thickness of the hydrophobic layer. The nanofiber composite in both two layers possesses a core-shell structure, guaranteeing the excellent flexibility and stretchability of the JM. In addition, the strong interfacial compatibility between the two layers ensures the stability and durability of the JM even after multiple stretching. More importantly, the JM could realize on-demand separation of different kinds of oily wastewater with high separation flux and separation efficiency, including oil/water mixtures with different oil densities, oil-in-water emulsions and water-in-oil emulsions. Furthermore, the JM exhibits cycling stability and long-term serviceability for the emulsion separation. The mechanically robust and stretchable JM has promising applications in purification of various oil contaminated wastewater.

Hierarchical porous metal–organic gels and derived materials: from fundamentals to potential applications

This review summarizes recent progress in the development and applications of metal–organic gels (MOGs) and their hybrids and derivatives dividing them into subclasses and discussing their synthesis, design and structure–property relationship.

Dye contaminated wastewater treatment through metal–organic framework (MOF) based materials

A complete discussion of MOFs and MOF composites such as MOF-based membranes, magnetic MOFs, and metal–organic gels (MOGs) used for dye removal along with their adsorption efficiency has been done.

Synchronous Construction of the Hierarchical Pores and High Hydrophobicity of Stable Metal-Organic Frameworks through a Dual Coordination-Competitive Strategy

Hierarchical-pore construction and functionalities are critical to further extend the applications of some stable MOFs, such as water remediation, fuel purification, oil/water separation, and self-cleaning, which are rarely achieved simultaneously. Herein, we demonstrate a method of synchronously constructing high-hydrophobicity Zr-based metal-organic frameworks with hierarchical pores (HP-UiO-66) through a dual coordination-competitive strategy. The addition of alkanoic acids and Zn²⁺ ions as coordination-competitors could reduce the coordinative degree between the ligand and Zr⁴⁺ ions to effectively induce defect formation. The resulting unsaturated Zr⁴⁺ ions could fully combine with the existing alkanoic acid with a long chain to afford HP-UiO-66 with high-hydrophobicity characteristics. In addition, the particle size of pristine UiO-66 could be adjusted effectively from around 280 to 120 nm using different alkanoic acids when Zn²⁺ ions are not added. This study provided a simple way for effectively controlling the morphology and structure of UiO-66 at the same time. Moreover, this kind of high-hydrophobicity HP-UiO-66 showed potential applications in oil/water separation and selective adsorption of organic mixtures.

Nanochannel {InZn}-Organic Framework with a High Catalytic Performance on CO2 Chemical Fixation and Deacetalization-Knoevenagel Condensation

The rare combination of In^III 5p and Zn^II 3d in the presence of a structure-oriented TDP^6- ligand led to a robust hybrid material of {(Me₂NH₂)[InZn(TDP)(OH₂)]·4DMF·4H₂O}_n (NUC-42) with the interlaced hierarchical nanochannels (hexagonal and cylindrical) shaped by six rows of undocumented [InZn(CO₂)₆(OH₂)] clusters, which represented the first 5p-3d nanochannel-based heterometallic metal-organic framework. With respect to the multifarious symbiotic Lewis acid-base and Brønsted acid sites in the high porous framework, the catalytic performance of activated NUC-42a upon CO₂ cycloaddition with styrene oxide was evaluated under solvent-free conditions with 1 atm of CO₂ pressure, which exhibited that the reaction could be well completed at ambient temperature within 48 h or at 60 °C within 4 h with high yield and selectivity. Moreover, because of the acidic function of metal sites and a central free pyridine in the TDP^6- ligand, deacetalization-Knoevenagel condensation of acetals and malononitrile could be efficiently facilitated by an activated sample of NUC-42a under lukewarm conditions.

Welding partially reduced graphene oxides by MOFs into micro-mesoporous hybrids for high-performance oil absorption

Partially reduced graphene oxides (PRGOs) with a small number of COOH groups remaining at the edges were interlocked by UiO-66-NH2 nanoparticles into hierarchical porous hybrids (PRGO@UiO-66-NH2) during the synthesis of UiO-66-NH2 in the presence of PRGOs, in which the UiO-66-NH2 nanoparticles provide micropores and the interlocked PRGO skeletons provide mesopores. The peak intensity of the functional groups on the PRGO@UiO-66-NH2 hybrids decrease greatly when compared with the GO@UiO-66-NH2 hybrids and the UiO-66-NH2 nanoparticles, and the number of -COOH at the edge of the PRGOs are approximately 6.3% after reduction, which is confirmed by the FT-IR and XPS results. When the PRGO@UiO-66-NH2 hybrids were embedded in their macropores via hydrogen bonding, melamine foams (MFs) were able to effectively absorb a variety of water-immiscible organic solvents from oil/water biphasic mixtures and, at the same time, suppress water infusion due to Cassie-state surface superhydrophobicity with a water contact angle of 154.2° in air. After 10 cycles, the PRGO@UiO-66-NH2-laden MFs exhibited water contact angles of 148.3°, which indicated that the composite MFs had excellent stability and recycling ability after 10 cycles. The PRGO@UiO-66-NH2-laden MFs had an oil absorption capacity of >10 000 wt% of the dry mass of absorbents and water absorption capacity of ≈1.76 wt% of the adsorbate, thus highlighting the high absorption selectivity of oil over water.

Bioinspired Design of Sericin/Chitosan/Ag@MOF/GO Hydrogels for Efficiently Combating Resistant Bacteria, Rapid Hemostasis, and Wound Healing

Due to the spread of drug-resistant bacteria in hospitals, the development of antibacterial dressings has become a strategy to control wound infections caused by bacteria. Here, we reported a green strategy for in situ biomimetic syntheses of silver nanoparticles@organic frameworks/graphene oxide (Ag@MOF-GO) in sericin/chitosan/polyvinyl alcohol hydrogel. Ag@MOF-GO was synthesized in situ from the redox properties of tyrosine residues in silk sericin without additional chemicals, similar to a biomineralization process. The sericin/chitosan/Ag@MOF-GO dressing possessed a high porosity, good water retention, and a swelling ratio. The hemolysis rate of the composite was 3.9% and the cell viability rate was 131.2%, which indicated the hydrogel possessed good biocompatibility. The composite also showed excellent lasting antibacterial properties against drug-sensitive and drug-resistant pathogenic bacteria. The composite possessed excellent hemostatic activity. The coagulation effect of the composite may be related to its effect on the red blood cells and platelets, but it has nothing to do with the activation of coagulation factors. An in vitro cell migration assay confirmed and an in vivo evaluation of mice indicated that the composite could accelerate wound healing and re-epithelialization. In summary, the composite material is an ideal dressing for accelerating hemostasis, preventing bacterial infection, and promoting wound healing.

Robust Graphene@PPS Fibrous Membrane for Harsh Environmental Oil/Water Separation and All-Weather Cleanup of Crude Oil Spill by Joule Heat and Photothermal Effect

The cleanup of oily wastewater and crude-oil spills is a global challenge. Traditional membrane materials are inefficient for oil/water separation under harsh conditions and limited by sorption speeds because of the high viscosity of crude oil. Herein, a kind of Graphene-wrapped polyphenylene sulfide fibrous membrane with superior chemical resistance and hydrophobicity for efficient oil/water separation and fast adsorption of crude oil all-weather is reported. The reduced graphene oxide (rGO)@polyphenylene sulfide (PPS) fibrous membrane can be applied in the various harsh conditions with Joule heating and solar heating. In addition, the oil(dichloromethane)/water separation flux of rGO@PPS reached 12 903 L m^-2h^-1, and the separation efficiency reached 99.99%. After 10 cycles, the rGO@PPS still performed high separation flux and filtration efficiency. More importantly, the rGO@PPS still retained its high conductivity, excellent filtration efficiency, and stable hydrophobicity after acid or alkali treatment. Moreover, the rGO@PPS can be heated by solar energy to absorb viscous crude oil during the day, while at night, the crude oil can be adsorbed by Joule heating. The time to adsorb crude oil can be reduced by 98.6% and 97.3% through Joule heating and solar heating, respectively. This all-weather utilization greatly increases the adsorption efficiency and effectively reduces energy consumption.