Advanced stimuli-responsive membranes for smart separation

pH-responsive membranes: Mechanisms, fabrications, and applications

Understanding the mechanisms of pH-responsiveness allows researchers to design and fabricate membranes with specific functionalities for various applications. The pH-responsive membranes (PRMs) are particular categories of membranes that have an amazing aptitude to change their properties such as permeability, selectivity and surface charge in response to changes in pH levels. This review provides a brief introduction to mechanisms of pH-responsiveness in polymers and categorizes the applied polymers and functional groups. After that, different techniques for fabricating pH-responsive membranes such as grafting, the blending of pH-responsive polymers/microgels/nanomaterials, novel polymers and graphene-layered PRMs are discussed. The application of PRMs in different processes such as filtration membranes, reverse osmosis, drug delivery, gas separation, pervaporation and self-cleaning/antifouling properties with perspective to the challenges and future progress are reviewed. Lastly, the development and limitations of PRM fabrications and applications are compared to provide inclusive information for the advancement of next-generation PRMs with improved separation and filtration performance.

Recycling Organic Dyes within the Metal-Organic Framework for Photothermal Conversion

The pursuit of a straightforward method to recycle organic dyes from effluents and repurpose them into valuable materials represents a highly sought-after yet huge challenge within the realms of chemistry, environment, and materials science. In this context, we employ a host-guest strategy that leverages the recycling of the rhodamine B molecule within the porous structure of a metal-organic framework to facilitate photothermal conversion. This achievement is realized through the electrostatic interaction, which then gives rise to remarkable selectivity and unparalleled uptake capacity for the cationic rhodamine B molecule. Capitalizing on this approach, the application of a columnar device and membrane technology for efficiently trapping rhodamine B molecules becomes feasible. On account of the aggregation effect resulting from the confined pore structure of the host matrix, the fluorescence emission of the encapsulated RhB molecules is significantly reduced, which consequently enhances the photothermal performance of the hybrid material through nonradiative transition. Moreover, the photothermal conversion achieved showcases a myriad of high-performance applications, including bacterial inhibition against Escherichia coli and seawater desalination.

Eu3+-Directed Supramolecular Metallogels with Reversible Quadruple-Stimuli Response Behaviors

Smart luminescent materials that have the ability to reversibly adapt to external environmental stimuli and possess a wide range of responses are continually emerging, which place higher demands on the means of regulation and response sites. Here, europium ions (Eu3+)-directed supramolecular metallogels are constructed by orthogonal self-assembly of Eu3+ based coordination interactions and hydrogen bonding. A new organic ligand (L) is synthesized, consisting of crown ethers and two flexible amide bonds-linked 1,10-phenanthroline moieties to coordinate with Eu3+. Synergistic intermolecular hydrogen bonding in L and Eu3+-L coordination bonding enable Eu3+ and L to self-assemble into shape-persistent 3D coordination metallogels in MeOH solution. The key to success is the utilization of crown ethers, playing dual roles of acting both as building blocks to build L with C2-symmetrical structure, and as the ideal monomer for increasing the energy transfer from L to Eu3+'s excited state, thus maintaining the excellent luminescence of metallogels. Interestingly, such assemblies show K+, pH, F-, and mechano-induced reversible gel-sol transitions and tunable luminescence properties. Above findings are useful in the studies of molecular switches, dynamic assemblies, and smart luminescent materials.

Recent advances in membrane technologies applied in oil-water separation

Effective treatment of oily wastewater, which is toxic and harmful and causes serious environmental pollution and health risks, has become an important research field. Membrane separation technology has emerged as a key area of investigation in oil-water separation research due to its high separation efficiency, low costs, and user-friendly operation. This review aims to report on the advances in the research of various types of separation membranes around emulsion permeance, separation efficiency, antifouling efficiency, and stimulus responsiveness. Meanwhile, the challenges encountered in oil-water separation membranes are examined, and potential research avenues are identified.

Sulfonated Chitosan Gel Membrane with Confined Amine Carriers for Stable and Efficient Carbon Dioxide Capture

Capturing carbon dioxide (CO2) from flue gases is a crucial step towards reducing CO2 emissions. Among the various carbon capture methods, facilitated transport membranes (FTMs) have emerged as a promising technology for CO2 capture owing to their high efficiency and low energy consumption in separating CO2. However, FTMs still face the challenge of losing mobile carriers due to weak interaction between the carriers and membrane matrix. Herein, we report a sulfonated chitosan (SCS) gel membrane with confined amine carriers for effective CO2 capture. In this structure, diethylenetriamine (DETA) as a CO2-mobile carrier is confined within the SCS gel membrane via electrostatic forces, which can react reversibly with CO2 and thus greatly facilitate its transport. The SCS ion gel membrane allows for the fast diffusion of amine carriers within it while blocking the diffusion of nonreactive gases, like N2. Thus, the prepared membrane exhibits exceptional CO2 separation capabilities when tested under simulated flue gas conditions with CO2 permeance of 1155 GPU and an ultra-high CO2/N2 selectivity of above 550. Moreover, the membrane retains a stable separation performance during the 170 h continuous test. The excellent CO2 separation performance demonstrates the high potential of gel membranes for CO2 capture from flue gas.

A review of stimuli-responsive polymer-based gating membranes

The formation and properties of smart (stimuli-responsive) membranes are reviewed, with a special focus on temperature and pH triggering of gating to water, ions, polymers, nanoparticles, or other molecules of interest. The review is organized in two parts, starting with all-smart membranes based on intrinsically smart materials, in particular of the poly(N-isopropylacrylamide) family and similar polymers. The key steps of membrane fabrication are discussed, namely the deposition into thin films, functionalization of pores, and the secondary crosslinking of pre-existing microgel particles into membranes. The latter may be free-standing and do not necessitate the presence of a porous support layer. The temperature-dependent swelling properties of polymers provide a means of controlling the size of pores, and thus size-sensitive gating. Throughout the review, we highlight "positive" (gates open) or "negative" (closed) gating effects with respect to increasing temperature. In the second part, the functionalization of porous organic or inorganic membranes of various origins by either microgel particles or linear polymer brushes is discussed. In this case, the key steps are the adsorption or grafting mechanisms. Finally, whenever provided by the authors, the suitability of smart gating membranes for specific applications is highlighted.

Tunable Band Engineering Management on Perovskite MAPbBr3 /COFs Nano-Heterostructures for Efficient S-S Coupling Reactions

Efficient artificial photosynthesis of disulfide bonds holds promises to facilitate reverse decoding of genetic codes and deciphering the secrets of protein multilevel folding, as well as the development of life science and advanced functional materials. However, the incumbent synthesis strategies encounter separation challenges arising from leaving groups in the ─S─S─ coupling reaction. In this study, according to the reaction mechanism of free-radical-triggered ─S─S─ coupling, light-driven heterojunction functional photocatalysts are tailored and constructed, enabling them to efficiently generate free radicals and trigger the coupling reaction. Specifically, perovskites and covalent organic frameworks (COFs) are screened out as target materials due to their superior light-harvesting and photoelectronic properties, as well as flexible and tunable band structure. The in situ assembled Z-scheme heterojunction MAPB-M-COF (MAPbBr3 = MAPB, MA+ = CH3 NH2 + ) demonstrates a perfect trade-off between quantum efficiency and redox chemical potential via band engineering management. The MAPB-M-COF achieves a 100% ─S─S─ coupling yield with a record photoquantum efficiency of 11.50% and outstanding cycling stability, rivaling all the incumbent similar reaction systems. It highlights the effectiveness and superiority of application-oriented band engineering management in designing efficient multifunctional photocatalysts. This study demonstrates a concept-to-proof research methodology for the development of various integrated heterojunction semiconductors for light-driven chemical reaction and energy conversion.

Review of the Perspectives and Study of Thermo-Responsive Polymer Gels and Applications in Oil-Based Drilling Fluids

Thermoresponsive polymer gels are a type of intelligent material that can react to changes in temperature. These materials possess excellent innovative properties and find use in various fields. This paper systematically analyzes the methods for testing and regulating phase transition temperatures of thermo-responsive polymer gels based on their response mechanism. The report thoroughly introduces the latest research on thermo-responsive polymer gels in oil and gas extraction, discussing their advantages and challenges across various environments. Additionally, it elucidates how the application limitations of high-temperature and high-salt conditions can be resolved through process optimization and material innovation, ultimately broadening the scope of application of thermo-responsive polymer gels in oil and gas extraction. The article discusses the technological development and potential applications of thermo-responsive polymer gels in oil-based drilling fluids. This analysis aims to offer researchers in the oil and gas industry detailed insights into future possibilities for thermo-responsive polymer gels and to provide helpful guidance for their practical use in oil-based drilling fluids.