MOF-Like 3D Graphene-Based Catalytic Membrane Fabricated by One-Step Laser Scribing for Robust Water Purification and Green Energy Production

Dynamic Regulation of Hydrogen Bonding Networks and Solvation Structures for Synergistic Solar-Thermal Desalination of Seawater and Catalytic Degradation of Organic Pollutants

Although solar steam generation strategy is efficient in desalinating seawater, it is still challenging to achieve continuous solar-thermal desalination of seawater and catalytic degradation of organic pollutants. Herein, dynamic regulations of hydrogen bonding networks and solvation structures are realized by designing an asymmetric bilayer membrane consisting of a bacterial cellulose/carbon nanotube/Co2(OH)2CO3 nanorod top layer and a bacterial cellulose/Co2(OH)2CO3 nanorod (BCH) bottom layer. Crucially, the hydrogen bonding networks inside the membrane can be tuned by the rich surface -OH groups of the bacterial cellulose and Co2(OH)2CO3 as well as the ions and radicals in situ generated during the catalysis process. Moreover, both SO42- and HSO5- can regulate the solvation structure of Na+ and be adsorbed more preferentially on the evaporation surface than Cl-, thus hindering the de-solvation of the solvated Na+ and subsequent nucleation/growth of NaCl. Furthermore, the heat generated by the solar-thermal energy conversion can accelerate the reaction kinetics and enhance the catalytic degradation efficiency. This work provides a flow-bed water purification system with an asymmetric solar-thermal and catalytic membrane for synergistic solar thermal desalination of seawater/brine and catalytic degradation of organic pollutants.

Optical-Propulsion Metastructures

Pulsed laser micropropulsion (PLMP) offers a promising avenue for miniature space craft, yet conventional propellants face challenges in balancing efficiency and stability. An optical-propulsion metastructure strategy using metal-organic frameworks (MOFs) is presented to generate graphene-metal metastructures (GMM), specifically GMM-(HKUST-1), which significantly enhances PLMP performance. This novel approach leverages the unique interaction between pulsed lasers and the precisely engineered GMMs-comprising optimized metal nanoparticle size, graphene layers, and inter-particle gaps-to boost both propulsion efficiency and stability. Experimental and numerical analyses reveal that GMM-(HKUST-1) achieves aspecific impulse of 1072.94 s, ablation efficiency of 51.22%, and impulse thrust per mass of 105.15 µN µg-1, surpassing traditional propellants. With an average particle size of ≈12 nm and a density of 0.958 g cm-3, these metastructures exhibit 99% light absorption efficiency and maintain stability under atmospheric and humid conditions. The graphene nanolayer efficiently absorbs and converts laser energy, while the metal nanostructures enhance light-matter interactions, promoting energy transfer and material stability. These findings suggest that this GMM-based optical-propulsion strategy can revolutionize microspacecraft propulsion and energy systems, offering significant advancements across various domains.

In situ confined encapsulation of ultrafine Fe2O3 nanoclusters in N/S co-doped graphene-based membranes for continuous chemical conversion

Membranes with catalytic function can provide an effective approach for simultaneously transforming reactants to industrial chemicals and separation. However, rational design of stable and high-quality catalytic membranes with controlled structure remains a big challenge. We report a strategy for in situ confined encapsulation of ultrafine Fe2O3 nanoclusters in nitrogen and sulfur co-doped graphene-based membranes for continuous chemical conversion. By manipulation of the active ferric catalytic center and surrounding coordination atoms in doped rGO nanosheets, multiple coordination structures were provided to achieve improved catalytic properties. Angstrom-level confined interlayer structure (∼8 Å) was constructed by external pressurization of Fe/NS-rGO nanosheets on membrane substrate, and the adsorption energy of 4-nitrophenol (4-NP) molecule between Fe/NS-rGO layers was much stronger than that in traditional nanometer-level confined space due to extra interactions, achieving the catalytic efficiency with a high Turnover Frequency (TOF) value (1596.0 h-1). The prepared ultrathin Fe/NS-rGO catalytic membrane also exhibited excellent water flux and rejection rate for small dye molecules, as well as long-term separation activity toward naphthol green B (NgB) for at least 130 h. The progress offers a viable route to the rational design of high-quality catalytic membranes with tailored structures and properties for wide applications.

Antifouling Asymmetric Block Copolymer Nanofilms via Freestanding Interfacial Polymerization for Efficient and Sustainable Water Purification

Membrane materials that resist nonspecific or specific adsorption are urgently required in widespread practical applications, such as water purification, food processing, and life sciences. In water purification, inevitable membrane fouling not only limits membrane separation performance, leading to a decline in both permeance and selectivity, but also remarkably increases operation requirements, and augments extra maintenance costs and higher energy consumption. In this work, we report a freestanding interfacial polymerization (IP) fabrication strategy for in situ creation of asymmetric block copolymer (BCP) nanofilms with antifouling properties, greatly outperforming the conventional surface post-modification approaches. The resultant free-standing asymmetric BCP nanofilms with highly-dense, highly-hydrophilic polyethylene glycol (PEG) brushes on one side, can be readily formed via a typical IP process of a well-defined double-hydrophilic BCP composed of a highly-efficient antifouling PEG block and a membrane-forming multiamine block. The asymmetric BCP nanofilms have been applied for efficient and sustainable natural water purification, demonstrating extraordinary antifouling capabilities accompanied with superior separation performance far beyond commercial polyamide nanofiltration membranes. The antifouling behaviors of asymmetric BCP nanofilms derived from the combined effect of the hydration layer, electrostatic repulsion and steric hindrance were further elucidated by water flux and fouling resistance in combination with all-atom molecular dynamics (MD) simulation. This work opens up a new avenue for the large-scale and low-cost creation of broad-spectrum, asymmetric membrane materials with diverse functional "defect-free" surfaces in real-world applications.

3D-Printed MOF Monoliths: Fabrication Strategies and Environmental Applications

Metal-organic frameworks (MOFs) have been extensively considered as one of the most promising types of porous and crystalline organic-inorganic materials, thanks to their large specific surface area, high porosity, tailorable structures and compositions, diverse functionalities, and well-controlled pore/size distribution. However, most developed MOFs are in powder forms, which still have some technical challenges, including abrasion, dustiness, low packing densities, clogging, mass/heat transfer limitation, environmental pollution, and mechanical instability during the packing process, that restrict their applicability in industrial applications. Therefore, in recent years, attention has focused on techniques to convert MOF powders into macroscopic materials like beads, membranes, monoliths, gel/sponges, and nanofibers to overcome these challenges.Three-dimensional (3D) printing technology has achieved much interest because it can produce many high-resolution macroscopic frameworks with complex shapes and geometries from digital models. Therefore, this review summarizes the combination of different 3D printing strategies with MOFs and MOF-based materials for fabricating 3D-printed MOF monoliths and their environmental applications, emphasizing water treatment and gas adsorption/separation applications. Herein, the various strategies for the fabrication of 3D-printed MOF monoliths, such as direct ink writing, seed-assisted in-situ growth, coordination replication from solid precursors, matrix incorporation, selective laser sintering, and digital light processing, are described with the relevant examples. Finally, future directions and challenges of 3D-printed MOF monoliths are also presented to better plan future trajectories in the shaping of MOF materials with improved control over the structure, composition, and textural properties of 3D-printed MOF monoliths.

Advancements in Nanoenabled Membrane Distillation for a Sustainable Water-Energy-Environment Nexus

The emergence of nano innovations in membrane distillation (MD) has garnered increasing scientific interest. This enables the exploration of state-of-the-art nano-enabled MD membranes with desirable properties, which significantly improve the efficiency and reliability of the MD process and open up opportunities for achieving a sustainable water-energy-environment (WEE) nexus. This comprehensive review provides broad coverage and in-depth analysis of recent innovations in nano-enabled MD membranes, focusing on their role in achieving desirable properties, such as strong liquid-repellence, high resistance to scaling, fouling, and wetting, as well as efficient self-heating and self-cleaning functionalities. The recent developments in nano-enhanced photothermal-catalytic applications for water-energy co-generation within a single MD system are also discussed. Furthermore, the bottlenecks are identified that impede the scale-up of nanoenhanced MD membranes and a future roadmap is proposed for their sustainable commercialiation. This holistic overview is expected to inspire future research and development efforts to fully harness the potential of nano-enabled MD membranes to achieve sustainable integration of water, energy, and the environment.

Advances of Electrochemical and Electrochemiluminescent Sensors Based on Covalent Organic Frameworks

Covalent organic frameworks (COFs), a rapidly developing category of crystalline conjugated organic polymers, possess highly ordered structures, large specific surface areas, stable chemical properties, and tunable pore microenvironments. Since the first report of boroxine/boronate ester-linked COFs in 2005, COFs have rapidly gained popularity, showing important application prospects in various fields, such as sensing, catalysis, separation, and energy storage. Among them, COFs-based electrochemical (EC) sensors with upgraded analytical performance are arousing extensive interest. In this review, therefore, we summarize the basic properties and the general synthesis methods of COFs used in the field of electroanalytical chemistry, with special emphasis on their usages in the fabrication of chemical sensors, ions sensors, immunosensors, and aptasensors. Notably, the emerged COFs in the electrochemiluminescence (ECL) realm are thoroughly covered along with their preliminary applications. Additionally, final conclusions on state-of-the-art COFs are provided in terms of EC and ECL sensors, as well as challenges and prospects for extending and improving the research and applications of COFs in electroanalytical chemistry.

Ionization Engineering of Hydrogels Enables Highly Efficient Salt-Impeded Solar Evaporation and Night-Time Electricity Harvesting

Interfacial solar evaporation holds immense potential for brine desalination with low carbon footprints and high energy utilization. Hydrogels, as a tunable material platform from the molecular level to the macroscopic scale, have been considered the most promising candidate for solar evaporation. However, the simultaneous achievement of high evaporation efficiency and satisfactory tolerance to salt ions in brine remains a challenging scientific bottleneck, restricting the widespread application. Herein, we report ionization engineering, which endows polymer chains of hydrogels with electronegativity for impeding salt ions and activating water molecules, fundamentally overcoming the hydrogel salt-impeded challenge and dramatically expediting water evaporating in brine. The sodium dodecyl benzene sulfonate-modified carbon black is chosen as the solar absorbers. The hydrogel reaches a ground-breaking evaporation rate of 2.9 kg m-2 h-1 in 20 wt% brine with 95.6% efficiency under one sun irradiation, surpassing most of the reported literature. More notably, such a hydrogel-based evaporator enables extracting clean water from oversaturated salt solutions and maintains durability under different high-strength deformation or a 15-day continuous operation. Meantime, on the basis of the cation selectivity induced by the electronegativity, we first propose an all-day system that evaporates during the day and generates salinity-gradient electricity using waste-evaporated brine at night, anticipating pioneer a new opportunity for all-day resource-generating systems in fields of freshwater and electricity.

Laser-Assisted Design of MOF-Derivative Platforms from Nano- to Centimeter Scales for Photonic and Catalytic Applications

Laser conversion of metal-organic frameworks (MOFs) has recently emerged as a fast and low-energy consumptive approach to create scalable MOF derivatives for catalysis, energy, and optics. However, due to the virtually unlimited MOF structures and tunable laser parameters, the results of their interaction are unpredictable and poorly controlled. Here, we experimentally base a general approach to create nano- to centimeter-scale MOF derivatives with the desired nonlinear optical and catalytic properties. Five three- and two-dimensional MOFs, differing in chemical composition, topology, and thermal resistance, have been selected as precursors. Tuning the laser parameters (i.e., pulse duration from fs to ns and repetition rate from kHz to MHz), we switch between ultrafast nonthermal destruction and thermal decomposition of MOFs. We have established that regardless of the chemical composition and MOF topology, the tuning of the laser parameters allows obtaining a series of structurally different derivatives, and the transition from femtosecond to nanosecond laser regimes ensures the scaling of the derivatives from nano- to centimeter scales. Herein, the thermal resistance of MOFs affects the structure and chemical composition of the resulting derivatives. Finally, we outline the "laser parameters versus MOF structure" space, in which one can create the desired and scalable platforms with nonlinear optical properties from photoluminescence to light control and enhanced catalytic activity.

Microreactor-based micro/nanomaterials: fabrication, advances, and outlook

Micro/nanomaterials are widely used in optoelectronics, environmental materials, bioimaging, agricultural industries, and drug delivery owing to their marvelous features, such as quantum tunneling, size, surface and boundary, and Coulomb blockade effects. Recently, microreactor technology has opened up broad prospects for green and sustainable chemical synthesis as a powerful tool for process intensification and microscale manipulation. This review focuses on recent progress in the microreactor synthesis of micro/nanomaterials. First, the fabrication and design principles of existing microreactors for producing micro/nanomaterials are summarized and classified. Afterwards, typical examples are shown to demonstrate the fabrication of micro/nanomaterials, including metal nanoparticles, inorganic nonmetallic nanoparticles, organic nanoparticles, Janus particles, and MOFs. Finally, the future research prospects and key issues of microreactor-based micro/nanomaterials are discussed. In short, microreactors provide new ideas and methods for the synthesis of micro/nanomaterials, which have huge potential and inestimable possibilities in large-scale production and scientific research.

Self-Supporting Nanoporous Copper Film with High Porosity and Broadband Light Absorption for Efficient Solar Steam Generation

Solar steam generation (SSG) is a potential technology for freshwater production, which is expected to address the global water shortage problem. Some noble metals with good photothermal conversion performance have received wide concerns in SSG, while high cost limits their practical applications for water purification. Herein, a self-supporting nanoporous copper (NP-Cu) film was fabricated by one-step dealloying of a specially designed Al98Cu2 precursor with a dilute solid solution structure. In-situ and ex-situ characterizations were performed to reveal the phase and microstructure evolutions during dealloying. The NP-Cu film shows a unique three-dimensional bicontinuous ligament-channel structure with high porosity (94.8%), multi scale-channels and nanoscale ligaments (24.2 ± 4.4 nm), leading to its strong broadband absorption over the 200-2500 nm wavelength More importantly, the NP-Cu film exhibits excellent SSG performance with high evaporation rate, superior efficiency and good stability. The strong desalination ability of NP-Cu also manifests its potential applications in seawater desalination. The related mechanism has been rationalized based upon the nanoporous network, localized surface plasmon resonance effect and hydrophilicity.

CuCo Nanoparticle, Pd(II), and l-Proline Trifunctionalized UiO-67 Catalyst for Three-Step Sequential Asymmetric Reactions

Metal-organic frameworks (MOFs) have become a promising support for different active sites to construct multifunctional and heterogeneous catalysts. However, the related investigation mainly focuses on introducing one or two active sites into MOFs and trifunctional catalysts have been very rarely reported. Herein, non-noble CuCo alloy nanoparticles, Pd²⁺, and l-proline, as encapsulated active species, functional organic linkers, and active metal nodes, respectively, were successfully decorated to UiO-67 to construct a chiral trifunctional catalyst by the one-step method, which was further applied to asymmetric three-step sequential oxidation of aromatic alcohols/Suzuki coupling/asymmetric aldol reactions with excellent oxidation and coupling performance (yields up to 95 and 96%, respectively), as well as good enantioselectivities (ee_anti value up to 73%) in asymmetric aldol reactions. The heterogeneous catalyst can be reused at least five times without obvious deactivation due to the strong interaction between the MOFs and the active sites. This work provides an effective strategy to construct multifunctional catalysts via the introduction and combination of three or more of active sites, including encapsulated active species, functional organic linkers, and active metal nodes, into stable MOFs.

A Novel P@SiO2 Nano-Composite as Effective Adsorbent to Remove Methylene Blue Dye from Aqueous Media

This work aims to prepare a novel phosphate-embedded silica nanoparticles (P@SiO₂) nanocomposite as an effective adsorbent through a hydrothermal route. Firstly, a mixed solution of sodium silicate and sodium phosphate was passed through a strong acidic resin to convert it into hydrogen form. After that, the resultant solution was hydrothermally treated to yield P@SiO₂ nanocomposite. Using kinetic studies, methylene blue (MB) dye was selected to study the removal behavior of the P@SiO₂ nanocomposite. The obtained composite was characterized using several advanced techniques. The experimental results showed rapid kinetic adsorption where the equilibrium was reached within 100 s, and the pseudo-second-order fitted well with experimental data. Moreover, according to Langmuir, one gram of P@SiO₂ nanocomposite can remove 76.92 mg of the methylene blue dye. The thermodynamic studies showed that the adsorption process was spontaneous, exothermic, and ordered at the solid/solution interface. Finally, the results indicated that the presence of NaCl did not impact the adsorption behavior of MB dye. Due to the significant efficiency and promising properties of the prepared P@SiO₂ nanocomposite, it could be used as an effective adsorbent material to remove various cationic forms of pollutants from aqueous solutions in future works.

Waste-Derived Catalysts for Water Electrolysis: Circular Economy-Driven Sustainable Green Hydrogen Energy

The sustainable production of green hydrogen via water electrolysis necessitates cost-effective electrocatalysts. By following the circular economy principle, the utilization of waste-derived catalysts significantly promotes the sustainable development of green hydrogen energy. Currently, diverse waste-derived catalysts have exhibited excellent catalytic performance toward hydrogen evolution reaction (HER), oxygen evolution reaction (OER), and overall water electrolysis (OWE). Herein, we systematically examine recent achievements in waste-derived electrocatalysts for water electrolysis. The general principles of water electrolysis and design principles of efficient electrocatalysts are discussed, followed by the illustration of current strategies for transforming wastes into electrocatalysts. Then, applications of waste-derived catalysts (i.e., carbon-based catalysts, transitional metal-based catalysts, and carbon-based heterostructure catalysts) in HER, OER, and OWE are reviewed successively. An emphasis is put on correlating the catalysts' structure-performance relationship. Also, challenges and research directions in this booming field are finally highlighted. This review would provide useful insights into the design, synthesis, and applications of waste-derived electrocatalysts, and thus accelerate the development of the circular economy-driven green hydrogen energy scheme.

Aqueous Two-Phase Interfacial Assembly of COF Membranes for Water Desalination

Aqueous two-phase system features with ultralow interfacial tension and thick interfacial region, affording unique confined space for membrane assembly. Here, for the first time, an aqueous two-phase interfacial assembly method is proposed to fabricate covalent organic framework (COF) membranes. The aqueous solution containing polyethylene glycol and dextran undergoes segregated phase separation into two water-rich phases. By respectively distributing aldehyde and amine monomers into two aqueous phases, a series of COF membranes are fabricated at water-water interface. The resultant membranes exhibit high NaCl rejection of 93.0-93.6% and water permeance reaching 1.7-3.7 L m^-2 h^-1 bar^-1, superior to most water desalination membranes. Interestingly, the interfacial tension is found to have pronounced effect on membrane structures. The appropriate interfacial tension range (0.1-1.0 mN m^-1) leads to the tight and intact COF membranes. Furthermore, the method is extended to the fabrication of other COF and metal-organic polymer membranes. This work is the first exploitation of fabricating membranes in all-aqueous system, confering a green and generic method for advanced membrane manufacturing.