Membrane-based helium recovery from natural gas faces a major challenge due to membrane plasticization, which increases permeances but reduces selectivities. Thermal crosslinking has emerged as a promising approach to enhance the plasticization resistance of membranes by restricting segmental mobility and creating welldefined microporosity for gas separation. Herein, we develop novel dual thermally crosslinked asymmetric hollow fiber membranes (HFMs) using a 4,4 '-diamino-2,2 '-biphenyldicarboxylic acid-containing copolyimide. Decarboxylation-based dual crosslinking is achieved through heat treatment at various temperatures, resulting in the generation of C-C covalent bonds. The interchain distance increases from 5.33 to 5.76 & Aring;, and the hierarchical pore size distributions exhibit ultra-micropore size between 5.6 and 6.8 & Aring; as well as micropore size between 7.0 and 9.5 & Aring;. Notably, the formation of stable C-C covalent bonds through dual crosslinking and the existence of bulky -CF3 groups in the 2,2 '-bis(trifluoromethyl)-4,4 '-biphenyldiamine moiety prevent substructure collapse by enhancing the chain rigidity and rotational barrier. Gas transport properties of the crosslinked HFMs are effectively tuned by adjusting the heat treatment temperatures. Particularly, the PI-TFMB-HF@400 membrane exhibits a He permeance of 25 GPU and He/CH4 selectivity of 269. Additionally, the crosslinked HFMs exhibit enhanced plasticization resistance. The PI-TFMB-HF@400 membrane, for instance, shows only a 24 % decrease in mixed-gas CO2/CH4 selectivity and an 80 % increase in mixed-gas [He/(CO2 + CH4)] selectivity when exposed to a high-pressure (40 bar) ternary mixed-gas feed of He/CO2/CH4 (0.3/49.7/50, v/v/v), and the mixed-gas [He/ (CO2 + CH4)] selectivity increases with temperature. The dual thermally crosslinked HFMs in this study demonstrate the potential for helium recovery from aggressive natural gas.

Designing an amine modified silica derived from coal fly ash (CFA) towards direct air CO2 capture (DAC) provides an economic way to manage increasing atmospheric CO2 concentration utilizing solid wastes. In this work, rod-like SBA-15 (SBA-15-R) and wheat-like SBA-15 (SBA-15-W) with distinct pore lengths are synthesized from CFA by controlling the synthesis conditions and then modified by PEI via the wet impregnation method. Their CO2 adsorption behaviors under sub-ambient conditions are investigated to explore their feasibility under aggressive conditions. The adsorbents with various silica morphologies exhibit distinctive CO2 adsorption performance under ambient and sub-ambient conditions. At 35°C under dry conditions, the CO2 adsorption capacity increases with amine loading. The CO2 adsorption capacity (qe) of SBA-15-W-PEI with long channels reaches the highest qe of 1.92 mmol/g with 70 wt.% PEI loading due to a large amount of strong chemisorption sites. Under the sub-ambient conditions (-20°C, 400 ppm), SBA-15-R-PEI30 with short channels having weaker CO2 diffusion resistance exhibits promising CO2 uptake of 0.83 mmol/g. These findings indicate that the ultra-dilute CO2 adsorption at ambient temperature requires an adsorbent with large amounts of adsorption sites, whereas the adsorbents for cold temperature application should reconcile amine loading with CO2 diffusion resistance inside pores. The co-adsorption of H2O and CO2 significantly improves CO2 capacity from 0.83 mmol/g and 1.92 mmol/g to 1.81 mmol/g and 3.48 mmol/g for SBA-15-R-PEI30 (-20°C, 400 ppm) and SBA-15-W-PEI70 (35°C, 400 ppm), respectively. Furthermore, the CFA derived SBA-15-PEI shows good cyclic stability during five consecutive TSA cycles. Preparing the amine silica adsorbents from coal fly ash potentially reduces the adsorbent cost of DAC devices. Moreover, the systematic exploration of amine silica adsorbents at a wide range of temperatures guides the design of high-performance CO2 adsorbents employed under various climatic conditions.

This review summarizes the performance of recently developed microporous polymers for practical industrial O2/N2 separations. The macromolecular design of innovative polymers of intrinsic porosity and derivatives is evaluated from the perspective of pore structure regulation for their outstanding O2/N2 separation performance. The structural groups that could fine-tune the free volume elements are examined to discern the promising moiety and architectures to improve size-based sieving. The long-term aging behaviors of the state-of-the-art macromolecules are also screened to explore the impacts of improved pore/free volume configuration. The strategies using thermal treatments to reset the structure of microporosity are inspected for their potential to improve the gas permeability or enhance size-specific molecular sieving, including the thermal rearrangement of polymeric membranes and pyrolyzed carbon molecular membranes using pre-crosslinked precursors and PIM-derived precursors. Membrane process design and optimization are summarized to evaluate the prospects of these novel membrane materials for large-scale industrial applications.

Mixed matrix membranes (MMMs) with one class of fillers always require high loadings to maximize gas permeability. The incompatibility between polymers and high content fillers causes non-selective interfacial voids in the MMMs and poor mechanical properties of MMMs. This work adopts two morphology distinct fillers with chemical similarity to achieve improved gas separation performance of Tröger’ base membranes without sacrificing their mechanical properties. The three-dimensional ZIF-8 nanoparticles are beneficial for membrane gas permeability. The addition of low content ZIF-8 nanosheets can greatly improve H2/CH4 and CO2/CH4 selectivities of the membranes. ZIF-8 particles and ZIF-8 nanosheets with similar chemical properties can mix more homogeneously and disperse well in the polymer matrix with expected hydrogen bonding interaction compared to mixed ZIF-8 and CuBDC nanosheets. Eventually, the resulting dual filler MMMs doped with 4 wt% ZIF-8 nanosheets and 10 wt% ZIF-8 nanoparticles have H2/CH4 ideal selectivity of 60 with H2 permeability of 426 Barrer, which is an increase of 18% and 102% over pure membranes, respectively. Moreover, the membrane has a significantly enhanced CO2/CH4 mixed gas selectivity of 68 at sub-ambient temperature, accompanied by temperature-dependent CO2-induced plasticization behavior. Mixing morphology distinct fillers with chemical similarity is proved to be an effective method to prepare a robust MMM at low filler amounts, and the synergistic effect on gas permeability and selectivity endows these dual filler MMMs with great H2/CH4 and CO2/CH4 separation performance.

Microporous polymers are uniquely attractive for membrane-mediated gas separations; however, conventional microporous polymers suffer a ubiquitous trade-off between gas permeability and selectivity, leading to bottlenecks in their practical applications. Functionalization of microporous polymers via molecule engineering is an effective way to enhance their gas separation performance and processability. This review outlines the research progress of ionization to improve the gas separation performance of typical microporous polymers (e.g., polymers of intrinsic microporosity (PIM), perfluorinated polymers, microporous polyimides, etc.) and summarizes the different ionization methods, including carboxylation, sulfonation, quaternization, and other ionization processes. Additionally, the review also explores the research progress of ionization to regulate the processability, microporosity, and gas separation properties of microporous polymers. Specifically, ionization can effectively tailor the microporosity, improve the solubility coefficients of gas molecules, especially CO2, and enhance gas selectivities. In addition, ionization can improve the processability of PIMs and enhance the membrane plasticization resistance. Ionic microporous polymers provide an essential platform for developing energy-efficient and high-performance gas separation membranes.

Superacid-catalyzed polymers of intrinsic microporosity have attracted increasing attention in membrane-mediated gas separation due to their good processability, facile polymerization procedure, and tunable microporosity and gas separation performance. In this study, we synthesized a series of new superacid-catalyzed polymers with fully ladder backbones and well-defined micropores using a one-pot condensation polymerization. The incorporation of a contorted spirobisindane building block facilitated the formation of highly microporous structures in the resulting polymers, enhancing their intrinsic microporosity and gas separation properties. Among the three SACPs, SACP-PhMe exhibited the largest d-spacing value, specific surface area, and pore volume due to its bulkiest side group. The gas separation performance of the SACP membranes surpassed several benchmark polymer membranes, with the SACP-PhMe membrane demonstrating excellent performance in separating CO2/CH4, H2/CH4, O2/N2, and H2/N2. The SACP-Me membrane exhibited the lowest porosity, making it less susceptible to CO2 absorption and showing superior plasticization resistance. The results highlight the promising gas separation properties of the SACPs and their potential for various gas separation applications, offering new opportunities for advanced polymer membrane design.

Hourglass-shaped or bimodally distributed microcavities enable both high gas permeabilities and selectivities for highly energy-efficient gas separations.

混合基质膜结合了无机填充材料和聚合物组分的双重优势,被认为是一种可同时增加渗透性和选择性的新型方法,有望解决传统聚合物膜的Trade-off效应.混合基质膜的气体分离性能主要依赖无机填充材料的分子筛分性质和高分子本身的化学结构,因此适当选择无机填充材料对于制备高性能的混合基质膜十分重要.金属有机骨架(MOF)作为一种新型多孔填料,具有比表面积大、密度小、孔隙率高和孔尺寸可调等优点,因此在气体吸附分离和气体储存等领域应用广泛,为新型混合基质膜带来良好的发展机遇.但混合基质膜的分离性能并不是简单地两相性能相加,在大多数情况下分离性能远低于材料模拟的预测理论值,造成这种非理想性的关键因素之一是MOF晶体和聚合物之间的界面缺陷,这可能导致界面非选择性空隙的形成、聚合物硬化和孔隙堵塞等界面问题,降低膜的分离性能.因此,实现MOF-聚合物基质间的界面作用调控以改善界面相容性是充分发挥MOF基混合基质膜气体分离潜力的关键.本工作综述了MOF基混合基质膜近五年关于不同类型界面作用调控的方法及策略,及其对气体分离性能的影响.最后,总结构建的界面作用对于混合基质膜性能的正面影响并提出当中存在的问题,为混合基质膜未来的发展提供指导,并激励研究人员采取更多的策略来解决目前的挑战.

Fabricating a membrane with high H2/CO2 separation performance at high temperatures is highly desired. Herein, a cross-linked zeolitic imidazolate framework 8/poly[2,2 & PRIME;-(1,4-naphthalene)-5,5 & PRIME;-bibenzimidazoles] (ZIF8/NPBI) mixed matrix membranes (MMMs) with tiny defects in ZIF-8 is fabricated via a phosphoric acid doping approach. The cross-linked NPBI chains and partially etched ZIF-8 by the acid result in significantly improved H2 permeability and H2/CO2 mixed gas selectivity. At 150 & DEG;C, compared to pure PBI membrane, the H2 permeability of the acid-treated 10% ZIF-8/NPBI membrane is enhanced from 39.97 Barrer to 98.36 Barrer, and the H2/CO2 mixed gas selectivity increases from 4.6 to 8.9, eventually exceeding the Robeson's upper bound predicted for 150 & DEG;C. When tested with the gas mixtures of 50% H2/50% CO2 continuously, the resulting membrane exhibits a stable H2 permeability of around 74 Barrer and H2/CO2 mixed gas selectivity of es8.69 at 150 & DEG;C for 24 h. This simple approach of improving H2 permeability and H2/CO2 mixed gas selectivity through crosslinking and etching provides a new approach for designing MMMs for H2/CO2 separation at high temperatures.

The recovery of helium from natural gas using membranes has attracted substantial attention, while very limited polymers were spun into hollow fibers and evaluated for realistic helium recovery. This work demonstrates the successful preparation of asymmetric and highly helium-selective hollow fiber membranes for the enrichment of helium from natural gas. A novel, aromatic copolyimide was designed and fabricated into hollow fiber membranes (HFMs) via the dry-jet/wet-quench spinning approach. The as-prepared HFMs display a He permeance of 85 GPU and high He-related gas selectivities of 140, 204, 448, and 609 for He/N2, He/CH4, He/C2H6, and He/C3H8 gas pairs, respectively. Particularly, ternary and quaternary mixed-gas permeation results reveal excellent light and heavy hydrocarbon resistance due to the competition between plasticization and gas sorption. The HFMs also demonstrated superior low-temperature gas separation performance and outstanding membrane gas separation stability, rendering them attractive for helium recovery.

Herein, we develop and investigate the performance of defect-free hollow fiber membranes (HFMs) based on a novel 6FDA-mPDA0.65-DABA0.3-TFMB0.05 copolyimide for helium separation from multi-component natural gas. The copolyimide is synthesized using a two-step condensation polymerization, and the hollow fiber membranes are fabricated using a dry-jet/wet-quench spinning approach. Thermal crosslinking of hollow fiber membranes is conducted to enhance plasticization resistance. The crosslinked membranes exhibit improved He selectivity (alpha(He/CH4) = 259) compared to the pristine hollow fiber membrane (alpha(He/CH4) = 210). Gas permeation tests are performed on the pristine and crosslinked hollow fiber membranes using pure-gas and mixed-gas at various pressures. The results demonstrate that the crosslinked membranes effectively resist plasticization even under high-pressure gas feeds containing CO2, light hydrocarbons, and heavy hydrocarbons. In contrast, the uncros-slinked membranes experience plasticization, dramatically decreasing selectivity. The findings provide valuable insights into the plasticization behavior of different impurity compounds in hollow fiber membranes and highlight the potential of thermal crosslinking as an effective strategy to improve the plasticization resistance of HFMs for He recovery. These defect-free and plasticization-resistant membranes hold promise for efficient He recovery from mixed-gas streams, offering a viable and energy-efficient alternative to traditional separation methods.

Thermally induced chemical crosslinking has attracted substantial attention for fabricating plasticization resistant membranes due to the facile structure tunability that enables the construction of robust and well-defined architecture for gas separation. In this study, we report a new series of dual thermally crosslinkable polyimides derived from 4,4 '-diamino-2,2 '-biphenyldicarboxylic acid (DCB) containing two carboxyl groups, and a systematic investigation of the thermal treatment above and below Tg demonstrated the decarboxylation-induced crosslinking. The dual thermally crosslinked membranes were insoluble in common organic solvents and maintained excellent mechanical properties. Due to the evolution of CO2 and collapse of chain segments during thermal treatment, the crosslinked membranes exhibited hierarchical microcavity size distribution featuring ultra-micropore size in the range of 2.0-6.0 angstrom and micropore size in the range of 6.5-10.0 angstrom. Gas transport properties of the crosslinked membranes were feasibly tuned through the chemical compositions and thermal treatment procedures. For instance, the CO2 permeability of crosslinked 6FDA-DAM0.7-TFMB0.1-DCB0.2 increased almost three-fold with only a slight decrease in CO2/CH4 selectivity. The crosslinked membranes also demonstrated superior plasticization resistance with mixed-gas feed pressure up to 40 bar and excellent lowtemperature gas separation performance at -30 degrees C, making them attractive for aggressive gas separations.

Polymers of intrinsic microporosity have attracted comprehensive attention in membrane-mediated gas separation because of their rigid and contorted structure that facilitates well-defined microporosity for fast and selective gas transport. We report a new macromolecular design synthesizes semi-ladder and fully-ladder polymers of intrinsic microporosity containing 9H-xanthene units by superacid-catalyzed Friedel-Crafts polymerization named SACPs. The prepared SACP membranes display high microporosity with amorphous chain packing structure, high FFV, and high BET surfaces areas. In particular, SACP-3 exhibited the most elevated BET surfaces area of 568 m(2)/g, fractional free volume (FFV) of 0.243, and bimodal micropore size distribution with two maxima at similar to 5 and similar to 8 angstrom, respectively. Due to its fully ladder architecture, SACP-3 exhibits highly permeable gas transport with CO2 permeability of 6497 Barrer and CO2/CH4 selectivity of 7.8, respectively. The microporosity and gas permeation properties of SACP membranes are also demonstrated to be highly tailorable by employing different monomers. The facile polymerization procedure, excellent solubility and processability, highly diverse tunability, and outstanding gas separation performance render SACP membranes attractive for many membrane mediated gas separation processes.

The anodic alumina oxide (AAO)porous membrane was treated with low-temperature air plasma to obtain superhydrophilic nanochannels. An oil-soluble ferrofluid was introduced on the AAO membrane,and an intelligent and controllable microreactor was constructed by adjusting the direction and strength of the external magnetic field. The intelligent microreactor has the characteristics of multilevel gating,high currentgating ratio,and long-term cycle stability. It was used in homogeneous and heterogeneous reactions and char. acterized by fluorescence spectrophotometer and scanning electron microscope. The results showed that the re. action products have different yields and structures under different gated states,and have good application prospects in the controllable reaction of microreactors.

The design of an intelligent nanofluidic system for regulating the transport of substances such as ions and molecules is significant for applications in biological sensing, drug delivery, and energy harvesting. However, the existing nanofluidic system faces challenges in terms of an uncontrollable transport speed for molecules and ions and also a complex preparation processes, low durability, and slow response rate. Herein, we demonstrate the use of a bioinspired ferrofluid-based nanofluid that can facilitate multilevel ultrafast-responsive ion and molecule transport with speed control. Specifically, we reversibly deform bulk ferrofluids using a magnet and wet/dewet the outer surface of superhydrophilic nanochannels for building a smart transport system. By changing the direction and strength of the external magnetic field, a speed control, ultrafast-responsive molecular transport (<0.1 s), and controlled current gating ratio are achieved owing to the different pattern changes of ferrofluids on the outer surface of nanochannels. We also illustrate a practical application of this strategy for antibacterial devices to control the transport of drug molecules in a programmed manner. These results suggest that molecule transport can be further complexified and quantified through an intelligent nanofluidic system.

Multifunctional droplets manipulation devices are in urgent need for various laboratory operations such as chemical reaction and biological analysis. However, most current techniques that achieved a controllable droplet transport system mainly rely on passive diffusion for mixing, limiting their practical applications. Here, we develop a magnetic controlled dimple on slippery surface (MCDSS) that enables arbitrary direction or even uphill droplet transport through the synergy between gravitational force and asymmetrical droplet deformation. Further experiments demonstrate that our system could also be used for stirring microdroplets and accelerating the mixing speed by more than one hundred times. In addition, the microstir strategy could help to avoid locally uneven production of precipitation or gas in heterogeneous reactions. This combination of droplet delivery and agitation may have a promising future for application in various fields, for example, laboratory-on-a-chip platforms and microengines.

Resistive strain sensors play a crucial role in the development of flexible and stretchable electronics because of their excellent sensitivity and conformability. However, such sensors suffer from poor durability because of the low adhesion strength between the solid conductive layer and polymer and the irreparable dry friction inside the conventional solid conductive layers. Here, inspired from the structures and excellent abrasion resistance of tear films on animal corneas, we demonstrate ultradurable strain sensors based on uniform self-healing wear-free liquid films formed on biomimetic microvilli made from modified polydimethylsiloxane (PDMS). Ethanol solutions containing ionic liquids (ILs) are added to PDMS microvilli, which are superlyophilic due to the surface chemistry and special structures. During evaporation, ILs are driven upward by Laplace pressure and join into continuous conductive films. As the sensing layer, when repeatedly stretched and released, the capillary-stabilized liquid film is lossless because of wet friction, and the cracks will recover completely after release due to the capillary-force-induced self-healing capability, allowing the strain sensors to exhibit high durability of over 22 500 loading-unloading cycles. This work presents an approach for the construction of ultradurable electronics.