High-performance microporous polymer membranes prepared by interfacial polymerization for gas separation

Nano-enabled gas separation membranes: Advancing sustainability in the energy-environment Nexus

Gas separation membranes serve as crucial to numerous industrial processes, including gas purification, energy production, and environmental protection. Recent advancements in nanomaterials have drastically revolutionized the process of developing tailored gas separation membranes, providing unreachable levels of control over the performance and characteristics of the membrane. The incorporation of cutting-edge nanomaterials into the composition of traditional polymer-based membranes has provided novel opportunities. This review critically analyses recent advancements, exploring the diverse types of nanomaterials employed, their synthesis techniques, and their integration into membrane matrices. The impact of nanomaterial incorporation on separation efficiency, selectivity, and structural integrity is evaluated across various gas separation scenarios. Furthermore, the underlying mechanisms behind nanomaterial-enhanced gas transport are examined, shedding light on the intricate interactions between nanoscale components and gas molecules. The review also discusses potential drawbacks and considerations associated with nanomaterial utilization in membrane development, including scalability and long-term stability. This review article highlights nanomaterials' significant impact in revolutionizing the field of selective gas separation membranes, offering the potential for innovation and future directions in this ever-evolving sector.

Dual-phase microporous polymer nanofilms by interfacial polymerization for ultrafast molecular separation

Fine-tuning microporosity in polymers with a scalable method has great potential for energy-efficient molecular separations. Here, we report a dual-phase molecular engineering approach to prepare microporous polymer nanofilms through interfacial polymerization. By integrating two micropore-generating units such as a water-soluble Tröger's base diamine (TBD) and a contorted spirobifluorene (SBF) motif, the resultant TBD-SBF polyamide shows an unprecedentedly high surface area. An ultrathin TBD-SBF membrane (~20 nm) exhibits up to 220 times improved solvent permeance with a moderate molecular weight cutoff (~640 g mol-1) compared to the control membrane prepared by conventional chemistry, which outperforms currently reported polymeric membranes. We also highlight the great potential of the SBF-based microporous polyamides for hydrocarbon separations by exploring the isomeric effects of aqueous phase monomers to manipulate microporosity.

Progress of research on the bonding-strength improvement of two-layer adhesive-free flexible copper-clad laminates

The arrival of the 5G era has placed high demands on the electronic products. Developing thin, light, and portable electronic products capable of simultaneously improving the transmission rate and reducing the signal delay and transmission loss is necessary to meet such demands. The traditional three-layer, adhesive, flexible copper-clad laminate (3L-FCCL) cannot satisfy these demands because of its adhesive component. The large thickness and poor heat resistance disadvantages of 3L-FCCL can be avoided with a two-layer, adhesive-free, flexible copper-clad laminate (2L-FCCL). However, 2L-FCCL has low bonding strength. This work introduces the selection of conductor materials and insulating base films for flexible copper-clad laminates. Modification studies aimed at increasing the bonding performance of 2L-FCCL are summarized based on three aspects. These modification techniques include the surface treatment of copper foils, modification and surface treatment of polyimide films, and surface treatment of liquid-crystal polymers. Prospects are further provided.

Graphene-grafted bimetallic MOF membranes for hazardous & toxic contaminants treatment

Development of membrane with improved carbon dioxide (CO2) gas separation capability is a significant challenge. However, the fabrication of membrane that efficiently separate and purification CO2-containing gases has been the focus of global attention. Cellulose Acetate (CA) has robust reinforcing characteristics when incorporated within a suitable polymer matrix. This work focus on the synthesis of novel mixed matrix membranes (MMMs) by introducing Graphene-grafted bimetallic MOFs in Cellulose Acetate polymer. The graphene-grafted bimetallic MOF (GG-BM MOFs) was prepared by a hydrothermal technique. Whereas, the solution casting approach used to fabricate membranes. The 1-5 wt% of GG-BM MOFs incorporated into the CA matrix. The mechanical, hydrophilicity and adsorption characteristics of fabricated MMMs were investigated. The crystallinity of MMM enhanced after the addition of GG-BM MOFs. In addition, the mechanical characteristics of MMMs were improved with the incorporation of GG-BM MOFs inside the polymer matrix. Maximum stress and strain was obtained for 2 wt% MMM (36.4 N/mm2 and 11% respectively). The CO2 adsorption performance was evaluated at 10 bar and 45 °C. The FTIR results represent insignificant bond shifting with the addition GG-BM MOFs at these conditions. The overall results showed that MMMs containing 2 wt% GG-BM MOFs have good adsorption properties for CO2 i.e 3.15 wt% of CO2. The MMMs have shown a decrease in the mechanical properties and CO2 adsorption at the higher GG-BM MOFs loading due to the presence of agglomeration which was confirmed through SEM. Thus, the addition of GG-BM MOFs in the CA matrix positively altered the physicochemical characteristics of the resulting MMMs, which could assist them in achieving remarkable CO2 adsorption at 2 wt%.

From the teapot effect to tap-triggered self-wetting: a 3D self-driving sieve for whole blood filtration

Achieving passive microparticle filtration with micropore membranes is challenging due to the capillary pinning effect of the membranes. Inspired by the teapot effect that occurs when liquid (tea) is poured from a teapot spout, we proposed a tap-triggered self-wetting strategy and utilized the method with a 3D sieve to filter rare cells. First, a 3D-printed polymer tap-trigger microstructure was implemented. As a result, the 3 µm micropore membrane gating threshold (the pressure needed to open the micropores) was lowered from above 3000 to 80 Pa by the tap-trigger microstructure that facilated the liquid leakage and spreading to self-wet more membrane area in a positive feedback loop. Then, we implemented a 3D cone-shaped cell sieve with tap-trigger microstructures. Driven by gravity, the sieve performed at a high throughput above 20 mL/min (DPBS), while the micropore size and porosity were 3 µm and 14.1%, respectively. We further filtered leukocytes from whole blood samples with the proposed new 3D sieve, and the method was compared with the traditional method of leukocyte isolation by chemically removing red blood cells. The device exhibited comparable leukocyte purity but a higher platelet removal rate and lower leukocyte simulation level, facilitating downstream single-cell analysis. The key results indicated that the tap-triggered self-wetting strategy could significantly improve the performance of passive microparticle filtration.

A New Look at the Structure and Thermal Behavior of Polyvinylidene Fluoride-Camphor Mixtures

An experimental quasi-equilibrium phase diagram of the polyvinylidene fluoride (PVDF)-camphor mixture is constructed using an original optical method. For the first time, it contains a boundary curve that describes the dependence of camphor solubility in the amorphous regions of PVDF on temperature. It is argued that this diagram cannot be considered a full analogue of the eutectic phase diagrams of two low-molar-mass crystalline substances. The phase diagram is used to interpret the polarized light hot-stage microscopy data on cooling the above mixtures from a homogeneous state to room temperature and scanning electron microscopy data on the morphology of capillary-porous bodies formed upon camphor removal. Based on our calorimetry and X-ray studies, we put in doubt the possibility of incongruent crystalline complex formation between PVDF and camphor previously suggested by Dasgupta et al. (Macromolecules 2005, 38, 5602-5608). We also describe and discuss the high-temperature crystalline structure of racemic camphor, which is not available in the modern literature.

Functionalized organic filler based integrated membranes for environmental remediation

Mixed matrix membranes (MMMs) are synthesized for efficient CO₂ separation released from various anthropogenic sources, which are due to global environmental concerns. The synergetic effect of porous nitrogen-rich, CO₂-philic filler and polymer in mixed matrix-based membranes (MMMs) can separate CO₂ competent. The development of various loadings of porphyrin poly(N-isopropyl Acryl Amide) (P-NIPAM)as functionalized organic fillers (5-20%) in polysulfone (PSU) through solution casting is carried out followed by the various characterizations including field emission scanning electron microscopy (FESEM), X-ray diffraction analysis (XRD), Fourier Transform Infrared Spectrometer(FT-IR) analysis and pure and mixed gas permeations ranging from 2 to 10 bar feed pressure. Due to both organic species interactions in the matrix, well-distributed fillers and homogenous surfaces, and cross-sectional structures were observed due to π-π interactions and Lewis's basic functionalities. The strong affinity of porous nitrogen-rich and CO₂-philic fillers through gas permeation analysis showed high CO₂/CH₄ and CO₂/N₂ gas performance that surpassed Robeson's upper bound limit. Comparatively, MMMs showed improved CO₂/CH₄ permeabilities from 87.5 ± 0.5 Barrer to 88.2 ± 0.9 Barrer than pure polymer matrix. For CO₂/N₂, CO₂ permeabilities improved to 75 ± 0.8 Barrer than pure polymer matrix. For both gas pairs (CO₂/CH₄, CO₂/N₂), respective pureselectivities (84%; 86%) and binary selectivities (85% and 85%)were improved. Various theoretical gas permeation models were used to predict CO₂ permeabilities for MMMs from which the modified Maxwell-Wagner-Sillar model showed the least AARE% of 0.87. The results showed promising results for efficient CO₂ separation due to exceptional functionalized P-PNIPAM affinitive properties. Finally, cost analysis reflected the inflated cost of membranes production for industrial setup using indigenous resources.

3D printed MOF-based mixed matrix thin-film composite membranes

MOF-based mixed-matrix membranes (MMMs) have attracted considerable attention due to their tremendous separation performance and facile processability. In large-scale applications such as CO₂ separation from flue gas, it is necessary to have high gas permeance, which can be achieved using thin membranes. However, there are only a handful of MOF MMMs that are fabricated in the form of thin-film composite (TFC) membranes. We propose herein the fabrication of robust thin-film composite mixed-matrix membranes (TFC MMMs) using a three dimensional (3D) printing technique with a thickness of 2-3 μm. We systematically studied the effect of casting concentration and number of electrospray cycles on membrane thickness and CO₂ separation performance. Using a low concentration of polymer of intrinsic microporosity (PIM-1) or PIM-1/HKUST-1 solution (0.1 wt%) leads to TFC membranes with a thickness of less than 500 nm, but the fabricated membranes showed poor CO₂/N₂ selectivity, which could be attributed to microscopic defects. To avoid these microscale defects, we increased the concentration of the casting solution to 0.5 wt% resulting in TFC MMMs with a thickness of 2-3 μm which showed three times higher CO₂ permeance than the neat PIM-1 membrane. These membranes represent the first examples of 3D printed TFC MMMs using the electrospray printing technique.

Multicomponent Spiropolymerization of Diisocyanides, Diethyl Acetylenedicarboxylate, and Halogenated Quinones

Multicomponent spiropolymerization (MCSP) provides an efficient synthetic tool for the construction of spiropolymers based on nonspiro monomers. In this study, a method of MCSP using diisocyanides 1, diethyl acetylenedicarboxylate 2, and halogenated quinones 3 is developed for the in situ construction of bis-spiropolymers with high molecular weights (M_w up to 29 200) and good yields (up to 87.7%) under mild reaction conditions. The structure of the obtained bis-spiropolymers is confirmed by gel permeation chromatography, Fourier transform infrared spectroscopy, and nuclear magnetic resonance analysis. Halogenated bis-spiropolymers show good thermal stability, good solubility, and film-forming ability. The photosensitizer rhodamine B is used as a doping agent to induce the photodegradation of the polymer P1a3c into small-molecule segments, which results in the slow release of halogenated spiro-groups under irradiation with simulated sunlight. This finding reveals that P1a3c has the potential to be applied in pesticides. Therefore, this MCSP is a novel method for preparing halogen-containing bis-spiropolymers, which accelerates the development of multifunctional polymer materials.

Recent Advances in Porphyrin-Based Materials for Metal Ions Detection

Porphyrins have planar and conjugated structures, good optical properties, and other special functional properties. Owing to these excellent properties, in recent years, porphyrins and their analogues have emerged as a multifunctional platform for chemical sensors. The rich chemistry of these molecules offers many possibilities for metal ions detection. This review mainly discusses two types of molecular porphyrin and porphyrin composite sensors for metal ions detection, because porphyrins can be functionalized to improve their functional properties, which can introduce more chemical and functional sites. According to the different application materials, the section of porphyrin composite sensors is divided into five sub-categories: (1) porphyrin film, (2) porphyrin metal complex, (3) metal–organic frameworks, (4) graphene materials, and (5) other materials, respectively.

Ultrathin permselective membranes: the latent way for efficient gas separation

Membrane gas separation has attracted the attention of chemical engineers for the selective separation of gases. Among the different types of membranes used, ultrathin membranes are recognized to break the trade-off between selectivity and permeance to provide ultimate separation. Such success has been associated with the ultrathin nature of the selective layer as well as their defect-free structure. These membrane features can be obtained from specific membrane preparation procedures used, in which the intrinsic properties of different nanostructured materials (e.g., polymers, zeolites, covalent-organic frameworks, metal-organic frameworks, and graphene and its derivatives) also play a crucial role. It is likely that such a concept of membranes will be explored in the coming years. Therefore, the goal of this review study is to give the latest insights into the use of ultrathin selective barriers, highlighting and describing the primary membrane preparation protocols applied, such as atomic layer deposition, in situ crystal formation, interfacial polymerization, Langmuir-Blodgett technique, facile filtration process, and gutter layer formation, to mention just a few. For this, the most recent approaches are addressed, with particular emphasis on the most relevant results in separating gas molecules. A brief overview of the fundamentals for the application of the techniques is given. Finally, by reviewing the ongoing development works, the concluding remarks and future trends are also provided.

Response Surface Methodology Optimization and Kinetic Study of Ultrafiltration-Enhanced, SCER-catalyzed Hydrolysis of Lard

The integration process of polyethersulphone (PES) ultrafiltration with catalytic hydrolysis of lard was optimized by response surface methodology (RSM). The influences of molar ratio of water to lard, reaction time and transmembrane pressure on the fatty acids (FAs) yield were investigated. Results showed that the maximum FAs yield of 99.52 % was obtained under the optimized conditions of molar ratio of water to lard of 6.0:1.0, reaction time of 10.0 h and transmembrane pressure of 100.0 kPa. Moreover, the membrane cleaning efficiency was studied after four cleanings. Furthermore, the kinetic model of membrane separation process was investigated and the activation energy and pre-exponential factor were determined.