Porous metal organic framework CuBDC nanosheet incorporated thin-film nanocomposite membrane for high-performance forward osmosis

Custom-designed 3D printed feed spacers and TFN membranes with MIL-101(Fe) for water recovery by forward osmosis

In this work, a dual-pronged approach- (i) novel thin-film nanocomposite polyether sulfone (PES) membrane with MIL-101 (Fe) and (ii) 3D printed spacers were explored to enhance water recovery by forward osmosis. The concentration of PES, pore former, draw solution, and MIL-101(Fe) was optimised for maximum pure water flux (PWF) and minimum specific reverse solute flux (SRSF). The best membrane exhibited a PWF of 7.52 Lm-2 h-1 and an SRSF of 0.33 ± 0.03 gL-1 using 1.5 M NaCl and DI water feed. The M22 membrane with the diamond-type spacer demonstrated a PWF of 2.53 Lm-2 h-1 and SRSF of 0.75 gL-1 for emulsified oily wastewater feed. The novel spacer design imparted significant turbulence to the feed flow and a lower foulant resistance of 1.3 m-1 as compared to the ladder type (1.5 m-1) or commercial spacer (1.7 m-1). This arrangement could recover 19% pure water within 12 h of operation (98% oil rejection) with a ∼ 94% flux recovery after hydraulic wash.

Progressive Insights into Metal-Organic Frameworks and Metal-Organic Framework-Membrane Composite Systems for Wastewater Management

The sustainable management of wastewater through recycling and utilization stands as a pressing concern in the trajectory of societal advancement. Prioritizing the elimination of diverse organic contaminants is paramount in wastewater treatment, garnering significant attention from researchers worldwide. Emerging metal-organic framework materials (MOFs), bridging organic and inorganic attributes, have surfaced as novel adsorbents, showcasing pivotal potential in wastewater remediation. Nevertheless, challenges like limited water stability, elevated dissolution rates, and inadequate hydrophobicity persist in the context of wastewater treatment. To enhance the performance of MOFs, they can be modified through chemical or physical methods, and combined with membrane materials as additives to create membrane composite materials. These membrane composites, derived from MOFs, exhibit remarkable characteristics including enhanced porosity, adjustable pore dimensions, superior permeability, optimal conductivity, and robust water stability. Their ability to effectively sequester organic compounds has spurred significant research in this field. This paper introduces methods for enhancing the performance of MOFs and explores their potential applications in water treatment. It delves into the detailed design, synthesis strategies, and fabrication of composite membranes using MOFs. Furthermore, it focuses on the application prospects, challenges, and opportunities associated with MOF composite membranes in water treatment.

MOF-Based Membranes for Remediated Application of Water Pollution

Membrane separation plays a crucial role in the current increasingly complex energy environment. Membranes prepared by metal-organic framework (MOF) materials usually possess unique advantages in common, such as uniform pore size, ultra-high porosity, enhanced selectivity and throughput, and excellent adsorption property, which have been contributed to the separation fields. In this comprehensive review, we summarize various designs and synthesized strategies of free-standing MOF and composite MOF-based membranes for water treatment. Special emphases are given not only on the effects of MOF on membrane performance, removal efficiencies, and elimination mechanisms, but also on the importance of MOF-based membranes for the applications of oily and micro-pollutant removal, adsorption, separation, and catalysis. The challenges and opportunities in the future for the industrial implementation of MOF-based membranes are also discussed.

Recent advances in surface tailoring of thin film forward osmosis membranes: A review

The recent advancements in fabricating forward osmosis (FO) membranes have shown promising results in desalination and water treatment. Different methods have been applied to improve FO performance, such as using mixed or new draw solutions, enhancing the recovery of draw solutions, membrane modification, and developing FO-hybrid systems. However, reliable methods to address the current issues, including reverse salt flux, fouling, and antibacterial activities, are still in progress. In recent decades, surface modification has been applied to different membrane processes, including FO membranes. Introducing nanochannels, bioparticles, new monomers, and hydrophilic-based materials to the surface layer of FO membranes has significantly impacted their performance and efficiency and resulted in better control over fouling and concentration polarization (CP) in these membranes. This review critically investigates the recent developments in FO membrane processes and fabrication techniques for FO surface-layer modification. In addition, this study focuses on the latest materials and structures used for the surface modification of FO membranes. Finally, the current challenges, gaps, and suggestions for future studies in this field have been discussed in detail.

Thin-Film Nanocomposite (TFN) Membranes for Water Treatment Applications: Characterization and Performance

Thin-film nanocomposite (TFN) membranes have been widely investigated for water treatment applications due to their promising performance in terms of flux, salt rejection, and their antifouling properties. This review article provides an overview of the TFN membrane characterization and performance. It presents different characterization techniques that have been used to analyze these membranes and the nanofillers within them. The techniques comprise structural and elemental analysis, surface and morphology analysis, compositional analysis, and mechanical properties. Additionally, the fundamentals of membrane preparation are also presented, together with a classification of nanofillers that have been used so far. The potential of TFN membranes to address water scarcity and pollution challenges is significant. This review also lists examples of effective TFN membrane applications for water treatment. These include enhanced flux, enhanced salt rejection, antifouling, chlorine resistance, antimicrobial properties, thermal stability, and dye removal. The article concludes with a synopsis of the current status of TFN membranes and future perspectives.

A review on optimistic development of polymeric nanocomposite membrane on environmental remediation

Current health and environmental concerns about the abundance and drawbacks of municipal wastewater as well as industrial effluent have prompted the development of novel and innovative treatment processes. A global shortage of clean water poses significant challenges to the survival of all life forms. For the removal of both biodegradable and non-biodegradable harmful wastes/pollutants from water, sophisticated wastewater treatment technologies are required. Polymer membrane technology is critical to overcoming this major challenge. Polymer matrix-based nanocomposite membranes are among the most popular in polymer membrane technology in terms of convenience. These membranes and their major components are environmentally friendly, energy efficient, cost effective, operationally versatile, and feasible. This review provides an overview of the drawbacks as well as promising developments in polymer membrane and nanocomposite membranes for environmental remediation, with a focus on wastewater treatment. Additionally, the advantages of nanocomposite membranes such as stability, antimicrobial properties, and adsorption processes have been discussed. The goal of this review was to summarize the remediation of harmful pollutants from water and wastewater/effluent using polymer matrix-based nanocomposite membrane technology, and to highlight its shortcomings and future prospects.

Review on Metal-Organic Framework Classification, Synthetic Approaches, and Influencing Factors: Applications in Energy, Drug Delivery, and Wastewater Treatment

Metal ions or clusters that have been bonded with organic linkers to create one- or more-dimensional structures are referred to as metal-organic frameworks (MOFs). Reticular synthesis also forms MOFs with properly designated components that can result in crystals with high porosities and great chemical and thermal stability. Due to the wider surface area, huge pore size, crystalline nature, and tunability, numerous MOFs have been shown to be potential candidates in various fields like gas storage and delivery, energy storage, catalysis, and chemical/biosensing. This study provides a quick overview of the current MOF synthesis techniques in order to familiarize newcomers in the chemical sciences field with the fast-growing MOF research. Beginning with the classification and nomenclature of MOFs, synthesis approaches of MOFs have been demonstrated. We also emphasize the potential applications of MOFs in numerous fields such as gas storage, drug delivery, rechargeable batteries, supercapacitors, and separation membranes. Lastly, the future scope is discussed along with prospective opportunities for the synthesis and application of nano-MOFs, which will help promote their uses in multidisciplinary research.

Recent advances in thin film nanocomposite membranes containing an interlayer (TFNi): fabrication, applications, characterization and perspectives

Polyamide (PA) reverse osmosis and nanofiltration membranes have been applied widely for desalination and wastewater reuse in the last 5-10 years. A novel thin-film nanocomposite (TFN) membrane featuring a nanomaterial interlayer (TFNi) has emerged in recent years and attracted the attention of researchers. The novel TFNi membranes are prepared from different nanomaterials and with different loading methods. The choices of intercalated nanomaterials, substrate layers and loading methods are based on the object to be treated. The introduction of nanostructured interlayers improves the formation of the PA separation layer and provides ultrafast water molecule transport channels. In this manner, the TFNi membrane mitigates the trade-off between permeability and selectivity reported for polyamide composite membranes. In addition, TFNi membranes enhance the removal of metal ions and organics and the recovery of organic solvents during nanofiltration and reverse osmosis, which is critical for environmental ecology and industrial applications. This review provides statistics and analyzes the developments in TFNi membranes over the last 5-10 years. The latest research results are reviewed, including the selection of the substrate and interlayer materials, preparation methods, specific application areas and more advanced characterization methods. Mechanistic aspects are analyzed to encourage future research, and potential mechanisms for industrialization are discussed.

Graphene Quantum Dot-Added Thin-Film Composite Membrane with Advanced Nanofibrous Support for Forward Osmosis

Forward osmosis (FO) technology for desalination has been extensively studied due to its immense benefits over conventionally used reverse osmosis. However, there are some challenges in this process such as a high reverse solute flux (RSF), low water flux, and poor chlorine resistance that must be properly addressed. These challenges in the FO process can be resolved through proper membrane design. This study describes the fabrication of thin-film composite (TFC) membranes with polyethersulfone solution blown-spun (SBS) nanofiber support and an incorporated selective layer of graphene quantum dots (GQDs). This is the first study to sustainably develop GQDs from banyan tree leaves for water treatment and to examine the chlorine resistance of a TFC FO membrane with SBS nanofiber support. Successful GQD formation was confirmed with different characterizations. The performance of the GQD-TFC-FO membrane was studied in terms of flux, long-term stability, and chlorine resistance. It was observed that the membrane with 0.05 wt.% of B-GQDs exhibited increased surface smoothness, hydrophilicity, water flux, salt rejection, and chlorine resistance, along with a low RSF and reduced solute flux compared with that of neat TFC membranes. The improvement can be attributed to the presence of GQDs in the polyamide layer and the utilization of SBS nanofibrous support in the TFC membrane. A simulation study was also carried out to validate the experimental data. The developed membrane has great potential in desalination and water treatment applications.

Solution Atomic Layer Deposition of Smooth, Continuous, Crystalline Metal-Organic Framework Thin Films

For the first time, a procedure has been established for the growth of surface-anchored metal-organic framework (SURMOF) copper(II) benzene-1,4-dicarboxylate (Cu-BDC) thin films of thickness control with single molecule accuracy. For this, we exploit the novel method solution atomic layer deposition (sALD). The sALD growth rate has been determined at 4.5 Å per cycle. The compact and dense SURMOF films grown at room temperature by sALD possess a vastly superior film thickness uniformity than those deposited by conventional solution-based techniques, such as dipping and spraying while featuring clear crystallinity from 100 nm thickness. The highly controlled layer-by-layer growth mechanism of sALD proves crucial to prevent unwanted side reactions such as Ostwald ripening or detrimental island growth, ensuring continuous Cu-BDC film coverage. This successful demonstration of sALD-grown compact continuous Cu-BDC SURMOF films is a paradigm change and provides a key advancement enabling a multitude of applications that require continuous and ultrathin coatings while maintaining tight film thickness specifications, which were previously unattainable with conventional solution-based growth methods.

Forward Osmosis Membranes: The Significant Roles of Selective Layer

Forward osmosis (FO) is a promising separation technology to overcome the challenges of pressure-driven membrane processes. The FO process has demonstrated profound advantages in treating feeds with high salinity and viscosity in applications such as brine treatment and food processing. This review discusses the advancement of FO membranes and the key membrane properties that are important in real applications. The membrane substrates have been the focus of the majority of FO membrane studies to reduce internal concentration polarization. However, the separation layer is critical in selecting the suitable FO membranes as the feed solute rejection and draw solute back diffusion are important considerations in designing large-scale FO processes. In this review, emphasis is placed on developing FO membrane selective layers with a high selectivity. The effects of porous FO substrates in synthesizing high-performance polyamide selective layer and strategies to overcome the substrate constraints are discussed. The role of interlayer in selective layer synthesis and the benefits of nanomaterial incorporation will also be reviewed.

Advances in metal-organic framework-based membranes

Membrane-based separations have garnered considerable attention owing to their high energy efficiency, low capital cost, small carbon footprint, and continuous operation mode. As a class of highly porous crystalline materials with well-defined pore systems and rich chemical functionalities, metal-organic frameworks (MOFs) have demonstrated great potential as promising membrane materials over the past few years. Different types of MOF-based membranes, including polycrystalline membranes, mixed matrix membranes (MMMs), and nanosheet-based membranes, have been developed for diversified applications with remarkable separation performances. In this comprehensive review, we first discuss the general classification of membranes and outline the historical development of MOF-based membranes. Subsequently, particular attention is devoted to design strategies for MOF-based membranes, along with detailed discussions on the latest advances on these membranes for various gas and liquid separation processes. Finally, challenges and future opportunities for the industrial implementation of these membranes are identified and outlined with the intent of providing insightful guidance on the design and fabrication of high-performance membranes in the future.

Polymer Nanocomposite Membrane for Wastewater Treatment: A Critical Review

With regard to global concerns, such as water scarcity and aquatic pollution from industries and domestic activities, membrane-based filtration for wastewater treatment has shown promising results in terms of water purification. Filtration by polymeric membranes is highly efficient in separating contaminants; however, such membranes have limited applications. Nanocomposite membranes, which are formed by adding nanofillers to polymeric membrane matrices, can enhance the filtration process. Considerable attention has been given to nanofillers, which include carbon-based nanoparticles and metal/metal oxide nanoparticles. In this review, we first examined the current status of membrane technologies for water filtration, polymeric nanocomposite membranes, and their applications. Additionally, we highlight the challenges faced in water treatment in developing countries.

Carbon Nanotube Interlayer Enhances Water Permeance and Antifouling Performance of Nanofiltration Membranes: Mechanisms and Experimental Evidence

Interlayered thin-film nanocomposite (TFNi) membranes have been shown to achieve enhanced water permeance as a result of the gutter effect. Nevertheless, some studies report impaired separation performance after the inclusion of an interlayer. In this study, we resolve the competing mechanisms of water transport in the transverse direction vs that in the normal direction. To enable easy comparison, carbon nanotube (CNT)-incorporated TFNi membranes with an identical polyamide rejection layer but different interlayer thicknesses were investigated. While increasing the thickness of the CNT interlayer facilitates water transport in the transverse direction (therefore improving the gutter effect), it simultaneously increases its hydraulic resistance in the normal direction. An optimal water permeance of 13.0 ± 0.7 L m^-2 h^-1 bar^-1, which was more than doubled over the control membrane of 6.1 ± 0.7 L m^-2 h^-1 bar^-1, was realized at a moderate interlayer thickness, resulting from the trade-off between these two competing mechanisms. In this study, we demonstrate reduced membrane fouling and improved fouling reversibility for a TFNi membrane over its control without an interlayer, which can be attributed to its more uniform water flux distribution. The fundamental mechanisms revealed in this study lay a solid foundation for the future development of TFNi membranes toward enhanced separation properties and antifouling ability.

Zwitterion-functionalized MIL-125-NH2-based thin-film nanocomposite forward osmosis membranes: towards improved performance for salt rejection and heavy metal removal

Incorporating zwitterion-functionalized MIL-125-NH2 nanoparticles in the rejection layer of TFN FO membranes improves their water/ion separation performance and antifouling ability.

Engineered two-dimensional nanomaterials: an emerging paradigm for water purification and monitoring

Water scarcity has become an increasingly complex challenge with the growth of the global population, economic expansion, and climate change, highlighting the demand for advanced water treatment technologies that can provide clean water in a scalable, reliable, affordable, and sustainable manner. Recent advancements on 2D nanomaterials (2DM) open a new pathway for addressing the grand challenge of water treatment owing to their unique structures and superior properties. Emerging 2D nanostructures such as graphene, MoS₂, MXene, h-BN, g-C₃N₄, and black phosphorus have demonstrated an unprecedented surface-to-volume ratio, which promises ultralow material use, ultrafast processing time, and ultrahigh treatment efficiency for water cleaning/monitoring. In this review, we provide a state-of-the-art account on engineered 2D nanomaterials and their applications in emerging water technologies, involving separation, adsorption, photocatalysis, and pollutant detection. The fundamental design strategies of 2DM are discussed with emphasis on their physicochemical properties, underlying mechanism and targeted applications in different scenarios. This review concludes with a perspective on the pressing challenges and emerging opportunities in 2DM-enabled wastewater treatment and water-quality monitoring. This review can help to elaborate the structure-processing-property relationship of 2DM, and aims to guide the design of next-generation 2DM systems for the development of selective, multifunctional, programmable, and even intelligent water technologies. The global significance of clean water for future generations sheds new light and much inspiration in this rising field to enhance the efficiency and affordability of water treatment and secure a global water supply in a growing portion of the world.

Copper-Modified Polymeric Membranes for Water Treatment: A Comprehensive Review

In the last decades, the incorporation of copper in polymeric membranes for water treatment has received greater attention, as an innovative potential solution against biofouling formation on membranes, as well as, by its ability to improve other relevant membrane properties. Copper has attractive characteristics: excellent antimicrobial activity, high natural abundance, low cost and the existence of multiple cost-effective synthesis routes for obtaining copper-based materials with tunable characteristics, which favor their incorporation into polymeric membranes. This study presents a comprehensive analysis of the progress made in the area regarding modified membranes for water treatment when incorporating copper. The notable use of copper materials (metallic and oxide nanoparticles, salts, composites, metal-polymer complexes, coordination polymers) for modifying microfiltration (MF), ultrafiltration (UF), nanofiltration (NF), forward osmosis (FO) and reverse osmosis (RO) membranes have been identified. Antibacterial and anti-fouling effect, hydrophilicity increase, improvements of the water flux, the rejection of compounds capacity and structural membrane parameters and the reduction of concentration polarization phenomena are some outstanding properties that improved. Moreover, the study acknowledges different membrane modification approaches to incorporate copper, such as, the incorporation during the membrane synthesis process (immobilization in polymer and phase inversion) or its surface modification using physical (coating, layer by layer assembly and electrospinning) and chemical (grafting, one-pot chelating, co-deposition and mussel-inspired PDA) surface modification techniques. Thus, the advantages and limitations of these modifications and their methods with insights towards a possible industrial applicability are presented. Furthermore, when copper was incorporated into membrane matrices, the study identified relevant detrimental consequences with potential to be solved, such as formation of defects, pore block, and nanoparticles agglomeration during their fabrication. Among others, the low modification stability, the uncontrolled copper ion releasing or leaching of incorporated copper material are also identified concerns. Thus, this article offers modification strategies that allow an effective copper incorporation on these polymeric membranes and solve these hinders. The article finishes with some claims about scaling up the implementation process, including long-term performance under real conditions, feasibility of production at large scale, and assessment of environmental impact.

Strategies in Forward Osmosis Membrane Substrate Fabrication and Modification: A Review

Forward osmosis (FO) has been recognized as the preferred alternative membrane-based separation technology for conventional water treatment technologies due to its high energy efficiency and promising separation performances. FO has been widely explored in the fields of wastewater treatment, desalination, food industry and bio-products, and energy generation. The substrate of the typically used FO thin film composite membranes serves as a support for selective layer formation and can significantly affect the structural and physicochemical properties of the resultant selective layer. This signifies the importance of substrate exploration to fine-tune proper fabrication and modification in obtaining optimized substrate structure with regards to thickness, tortuosity, and porosity on the two sides. The ultimate goal of substrate modification is to obtain a thin and highly selective membrane with enhanced hydrophilicity, antifouling propensity, as well as long duration stability. This review focuses on the various strategies used for FO membrane substrate fabrication and modification. An overview of FO membranes is first presented. The extant strategies applied in FO membrane substrate fabrications and modifications in addition to efforts made to mitigate membrane fouling are extensively reviewed. Lastly, the future perspective regarding the strategies on different FO substrate layers in water treatment are highlighted.

Constructing interlayer to tailor structure and performance of thin-film composite polyamide membranes: A review

Thin-film composite (TFC) structured membranes based on polyamide (PA) chemistry is the gold standard of nanofiltration and reverse osmosis-based technologies for water purification and desalination. Constructing interlayer between porous substrate and PA layer is a promising strategy to address the ubiquitous trade-off between permeability and selectivity, which is typically encountered by conventional TFC PA membranes. The progress in the interlayer benefits the precise control of interfacial polymerization process, which therefore can tailor the structure and performance of advanced TFC PA membranes. This review critically summarizes the recent advances in TFC PA membranes mediated by interlayer. The mechanisms of interlayer regulating the IP process and PA structure are first discussed based on available literature. Structure and performance of novel TFC PA membranes based on three kinds of interlayers, i.e., organic coatings, nanomaterial and nanocomposite interlayers, are systematically reviewed. Finally, perspectives and future efforts needed are proposed for interlayer based TFC PA membranes. This review offers comprehensive understanding and useful guidance on the rational design of advanced membranes mediated by interlayers for desalination and water purification.

MOFs for the treatment of arsenic, fluoride and iron contaminated drinking water: A review

Over the last few decades, the global pollution of surface and groundwater poses a serious threat not only to human beings but also towards aquatic lives due to the presence of emerging contaminants. Among the others, the presence of arsenic, fluoride, and iron are considered as the most common toxic pollutants in water bodies. The emergence of metal organic frameworks (MOFs) with high porosity and surface area is represented as significant inclusion into the era of entrapping contaminants present in drinking water. In the present review article, an in-depth insight is provided on the recent developments in the removal of arsenic, fluoride, and iron from drinking water using MOFs. Various aspects related to the synthesis, latest technologies adopted for the modifications in the synthesis process and advanced applications of MOFs for the removal of such contaminants are explicitly discussed. A detailed insight was provided to understand the mechanism of various interactions of MOFs with arsenic and fluoride. With respect to arsenic, fluoride, and iron removal the ultrastructural morphology of MOFs is assessed based on different molecular arrangements. Further, commercial aspects of various MOFs are presented in order to highlight the process feasibility. Finally, various perspectives and challenges involved in process scale up are comprehensively narrated with an aspiration of futuristic developments. The paper will be beneficial to the readers for acquiring a piece of in-depth knowledge on MOFs and its various synthesis approaches along with remarkable achievements for the removal of arsenic, fluoride, and iron from contaminated drinking water.

Fabrication of High-Performance Thin-Film Composite Nanofiltration Membrane by Dynamic Calcium-Carboxyl Intra-Bridging during Post-Treatment

Widespread applications of nanofiltration (NF) and reverse osmosis (RO)-based processes for water purification and desalination call for high-performance thin-film composite (TFC) membranes. In this work, a novel and facile modification method was proposed to fabricate high-performance thin-film composite nanofiltration membrane by introducing Ca2+ in the heat post-treatment. The introduction of Ca2+ induced in situ Ca2+-carboxyl intra-bridging, leading to the embedment of Ca2+ in the polyamide (PA) layer. This post modification enhanced the hydrophilicity and surface charge of NF membranes compared to the pristine membrane. More interestingly, the modified membrane had more nodules and exhibited rougher morphology. Such changes brought by the addition of Ca2+ enabled the significant increase of water permeability (increasing from 17.9 L·m-2·h-1·bar-1 to 29.8 L·m-2·h-1·bar-1) while maintaining a high selectivity (Na2SO4 rejection rate of 98.0%). Furthermore, the intra-bridging between calcium and carboxyl imparted the NF membranes with evident antifouling properties, exhibiting milder permeability decline of 4.2% (compared to 16.7% of NF-control) during filtration of sodium alginate solution. The results highlight the potential of using Ca2+-carboxyl intra-bridging post-treatment to fabricate high-performance TFC membranes for water purification and desalination.

Dually Charged MOF-Based Thin-Film Nanocomposite Nanofiltration Membrane for Enhanced Removal of Charged Pharmaceutically Active Compounds

Removal of pharmaceutically active compounds (PhACs) is of great importance in wastewater reclamation due to their potent negative impacts on human health. Typical polyamide nanofiltration (NF) membranes are negatively charged, which compromises their rejection rate of positively charged PhACs. Herein, we propose to rationally design a novel thin-film nanocomposite (TFN) NF membrane featuring a dually charged metal organic framework (MOF) to effectively remove both positively and negatively charged PhACs. Ethylenediamine (ED) was grafted to the coordinately unsaturated metal sites inside the MIL-101(Cr). The resulting ED-MIL-101(Cr) contained both strong positively charged amine groups inside its channels and negatively charged carboxyl groups at its surface. This dually charged nature of the MOF nanoparticles enabled the ED-MIL-101(Cr)-containing TFN membrane to achieve high rejection rates (mostly >90%) for both positively (terbutaline, atenolol, fluoxetine) and negatively charged PhACs (ketoprofen, diclofenac, bezafibrate). At the same time, the ED-MIL-101(Cr) TFN membrane had greatly improved water permeance (140% over the control membrane with MOF loading). Calculations based on density functional theory further confirmed the large energy barrier for the migration of both negatively and positively charged PhACs across the nanochannels of ED-MIL-101(Cr). This study highlights a promising potential of dually charged MOF-TFN membranes for efficient removal of trace organic contaminants in wastewater reclamation.

Practical MOF Nanoarchitectonics: New Strategies for Enhancing the Processability of MOFs for Practical Applications

Over the past decades, the development of porous materials has directly or indirectly affected industrial production methods. Metal-organic frameworks (MOFs) as an emerging class of porous materials exhibit some unique advantages, including controllable composition, a large surface area, high porosity, and so on. These attractive characteristics of MOFs have led to their potential applications in energy storage and conversion devices, drug delivery, adsorption and storage, sensors, and other areas. However, powdered MOFs have limited practical applications owing to poor processability, safety hazards from dust formation, and poor recyclability. In addition, the inherent micro/mesoporosities of MOFs also reduce the accessibility and diffusion kinetics for large molecules. To improve their processability for practical applications, MOFs are often deposited as MOF layers or films (i.e., MOF-coated composites) on supporting materials or are formed into 3D structured composites, such as aerogels and hydrogels. In this article, we review recent researches on these MOF composites, including their synthetic methods and potential applications in energy storage devices, heavy metal ion adsorption, and water purification. Finally, the future outlook and challenges associated with the large-scale fabrication of MOF-based composites for practical applications are discussed.

Factors Affecting the Performance of Membrane Osmotic Processes for Bioenergy Development

Forward osmosis (FO) and pressure-retarded osmosis (PRO) have gained attention recently as potential processes to solve water and energy scarcity problems with advantages over pressure-driven membrane processes. These processes can be designed to produce bioenergy and clean water at the same time (i.e., wastewater treatment with power generation). Despite having significant technological advancement, these bioenergy processes are yet to be implemented in full scale and commercialized due to its relatively low performance. Hence, massive and extensive research has been carried out to evaluate the variables in FO and PRO processes such as osmotic membrane, feed solutions, draw solutions, and operating conditions in order to maximize the outcomes, which include water flux and power density. However, these research findings have not been summarized and properly reviewed. The key parts of this review are to discuss the factors influencing the performance of FO and PRO with respective resulting effects and to determine the research gaps in their optimization with the aim of further improving these bioenergy processes and commercializing them in various industrial applications.

Theory and simulation developments of confined mass transport through graphene-based separation membranes

The perspectives of graphene-based membranes based on confined mass transport from simulations and experiments for water desalination.

Porous Zr-Based Metal-Organic Frameworks (Zr-MOFs)-Incorporated Thin-Film Nanocomposite Membrane toward Enhanced Desalination Performance

Four different thin-film nanocomposite (TFN) membranes were prepared by adding different concentrations of porous Zr-metal-organic frameworks (MOFs) (UiO-66 and UiO-66-NH₂) to piperazine aqueous solution (aqueous phase) or 1,3,5-benzenetricarbonyl trichloride-n-hexane solution (organic phase) by interfacial polymerization. The main purpose is to study the specific effects of different addition methods and addition amounts of nanoparticles on the structure and performance of the TFN membranes by interfacial polymerization. All four TFN membranes exhibited a higher water permeability while maintaining high salt rejection compared to thin-film composite membrane. On the one hand, the TFN membranes behave differently, which are prepared by adding the same kind of nanoparticles to the aqueous phase or organic phase, respectively. The TFN membrane prepared by adding 0.2 w/v% UiO-66 to the organic phase had a high water flux of 87.86 L m^-2 h^-1, compared to 46.31 L m^-2 h^-1 of the membrane prepared by adding 0.3 w/v% UiO-66 in the aqueous phase. This is due to the fact that UiO-66 greatly slows the interfacial polymerization rate when UiO-66 is added to the organic phase, resulting in a thinner and wider-aperture polyamide thin-film layer, reducing the water transmission resistance during filtration. Therefore, it is more economical by adding nanoparticles to organic phase than aqueous phase under the same filtering effect. On the other hand, different nanoparticles can also cause differences in performance and structure of the TFN membranes even in the same preparation manner. TFN membrane with UiO-66-NH₂ in the aqueous phase has higher water permeance than the one with UiO-66 in the aqueous phase, owing to the good hydrophilicity of the amino group, which improves the water dispersibility of UiO-66-NH₂ so that the TFN membrane is more uniform. In addition, UiO-66-NH₂ slows down the process of interface polymerization, making the membrane more porous. The monomers in the aqueous phase and organic phase can be adsorbed in the pores of Zr-MOFs, which makes the interfacial polymerization occur both in the pores and on the surface of the pores. Thus, the compatibility between the polyamide and MOFs was enhanced and less defects were formed in the thin-film layer, resulting in a high salt rejection even when the concentration of Zr-MOFs increased. This is the first time to explain that polyamide membrane has not obvious salt rejection attenuation with increasing porous material content using pore adsorption reaction monomer principle. Also, the Zr-MOFs-based TFN membrane exhibited good heat resistance and antifouling property. This work shows that porous Zr-MOFs nanomaterials have significant advantages in the development of nanofiltration membranes with high water flux and rejection.

Hydrophilic Selective Nanochannels Created by Metal Organic Frameworks in Nanofiltration Membranes Enhance Rejection of Hydrophobic Endocrine-Disrupting Compounds

Rejection of endocrine-disrupting compounds (EDCs) by thin-film composite (TFC) polyamide membranes remains a challenging issue in wastewater reclamation applications because of the unfavorable hydrophobic interaction between EDCs and membranes. Herein, we investigated the incorporation of hydrophilic metal organic frameworks (MOFs) into the polyamide layer to create water/EDC selective nanochannels for enhancing EDC rejection. Using MIL-101(Cr) MOF as a nanofiller, the water flux of the MOF0.20 TFC membrane (0.20 wt/v % MOF in n-hexane) was 2.3 times that of the control. The rejection rates against EDCs involving methylparaben, propylparaben, benzylparaben, and bisphenol A (BPA) by MOF0.20 were also significantly higher than the respective values of the control membrane, with the water/EDC selectivity (e.g., A/B_BPA) of MOF0.20 approximately doubled compared to that of the control. Further single salt rejection and gold nanoparticle filtration tests confirmed that the hydrophilic nanochannels created by MOFs played a critical role in membrane transport, accounting for the significant enhancement of EDC rejection of the modified TFC membrane. This study demonstrates a promising membrane modification protocol using hydrophilic MOFs for achieving selective removal of EDCs and high-efficient wastewater reclamation using TFC membranes.

Fabrication of a Novel Nanofiltration Membrane with Enhanced Performance via Interfacial Polymerization through the Incorporation of a New Zwitterionic Diamine Monomer

It is known that the polyamide (PA) barrier layer's inherent microstructure and surface physicochemical properties of thin film composite nanofiltration membrane are crucial for its separation performance. Herein, we designed and synthesized a new zwitterionic aromatic diamine monomer 3-(4-(2-((4-aminophenyl)amino)ethyl)morpholino-4-ium)propane-1-sulfonate (PPD-MEPS) through a three steps reaction, and this hydrophilic molecule was incorporated into the active layer to tailor the poly(piperazine-amide)-based nanofiltration membranes with significantly improved water permeability and antifouling properties. As a p-phenylenediamine (PPD) derivative, PPD-MEPS possesses two active amine units, which can react with trimesoyl chloride in the organic phase during the interfacial polymerization reaction process. Thus, the super-hydrophilic zwitterions were not only on the membrane surface but also across the whole PA layer to facilitate water molecule transportation. The successful augmentation of zwitterions into the PA layer was well illustrated by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR) results and X-ray photoelectron spectroscopy analysis. With increasing loading content of PPD-MEPS in PIP aqueous solution, the as-fabricated nanofiltration membranes (NFMs) exhibited higher hydrophilicity, increased active layer thickness, and molecular weight cut off. When the zwitterionic monomer reached 60% to PIP for NFM-4, the water permeability went up to 9.82 L m^-2 h^-1 bar^-1, increasing by 45%; meanwhile, the Na₂SO₄/NaCl selectivity increased from 2.54 to 4.03. In addition, the fouling experiments illustrated that the fouling resistance of the zwitterion-modified NFMs to bovine serum albumin was significantly improved.