Despite the rapid development of molecular rotors over the past decade, it still remains a huge challenge to understand their confined behavior in ultrathin two-dimensional (2D) nanomaterials for ...molecular recognition. Here, we report an all-carbon, 2D π-conjugated aromatic polymer, named NUS-25, containing flexible tetraphenylethylene (TPE) units as aggregation-induced emission (AIE) molecular rotors. NUS-25 bulk powder can be easily exfoliated into micrometer-sized lamellar freestanding nanosheets with a thickness of 2–5 nm. The dynamic behavior of the TPE rotors is partially restricted through noncovalent interactions in the ultrathin 2D nanosheets, which is proved by comparative experimental studies including AIE characteristics, size-selective molecular recognition, and theoretical calculations of rotary energy barrier. Because of the partially restricted TPE rotors, NUS-25 nanosheets are highly fluorescent. This property allows NUS-25 nanosheets to be used as a chemical sensor for the specific detection of acenaphthylene among a series of polycyclic aromatic hydrocarbons (PAHs) via fluorescent quenching mechanism. Further investigations show that NUS-25 nanosheets have much higher sensitivity and selectivity than their stacked bulk powder and other similar polymers containing dynamic TPE rotors. The highly efficient molecular recognition can be attributed to the photoinduced electron transfer (PET) from NUS-25 nanosheets to acenaphthylene, which is investigated by time-resolved photoluminescence measurements (TRPL), excitation and emission spectra, and density functional theory (DFT) calculations. Our findings demonstrate that confinement of AIE molecular rotors in 2D nanomaterials can enhance the molecular recognition. We anticipate that the material design strategy demonstrated in this study will inspire the development of other ultrathin 2D nanomaterials equipped with smart molecular machines for various applications.
Although precise design has advanced the separation capability of polymer membranes, the inability to maintain their performance under real process conditions involving elevated pressures and ...moisture has prevented their smooth transition into practical applications. Specifically, plasticization of polymers is a unique challenge to membrane-based CO2 separation. Herein, we show that the dispersion of a flexible metal-organic framework (MOF) within a polymer matrix allows the retention of high gas separation selectivity even at a transmembrane pressure of 12 bar, which is highly desirable for practical applications involving compressed feed streams. The strong interactions between MOF fillers and polymer matrices reduce the chain mobility of polymer, contributing to the enhanced plasticization resistance. X-ray diffraction (XRD) analysis indicates that channel closure of the flexible MOF in polymer is avoided, also suggesting strong MOF-polymer interactions. Importantly, observation of XRD-detectable phase changes in flexible MOFs is a useful strategy to reveal the interactions between flexible MOFs and the matrices.
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•The plasticization resistance of polymer membranes was enhanced by adding metal-organic framework (MOF) fillers.•The strong MOF-polymer interactions were demonstrated by X-ray diffraction characterization.•The preferential CO2 adsorption of MOFs enables an enhancement of separation performance.
Fiber-shaped supercapacitors (FSSCs), as a very new variety of flexible power source, are strongly needed for smart electronics, but the preparation still remains challenging. In this study, using ...silk fiber (SF) as a linear substrate, reduced graphene oxide (rGO) as an electron transport enhancing layer, and polypyrrole (PPy) as a pseudocapacitive wrapping phase, a PPy/rGO/SF ternary electrode is developed by a facile ‘dipping and drying’ and in situ polymerization. In three-electrode, the product depicts an attractive length specific capacitance of 85.9 mF cm
− 1
at 0.5 mA cm
− 1
, which represents a novel performance record in the SF based flexible electrodes, and is also even higher than a lot of carbon yarn and metal fiber based electrodes. The quasi-solid-state FSSC device, PPy/rGO/SF//PPy/rGO/SF, shows a high energy density of 2.2 µWh cm
− 1
at 25.9 µW cm
− 1
, and an outstanding power density of 438.8 µW cm
− 1
at 0.4 µWh cm
− 1
. Moreover, good capacitive stability and mechanical flexibility with capacitance retentions of 75% after 4000 charging/discharging cycles and 94% at bending degrees from 0 to 150° are presented. Our study supplies a good example for the preparation of high-performance SF electrode, which may contribute to the rapid development of FSSCs.
Water-bath microwave method was used for hydroxyl ammonium ionic liquids (ILs) synthesis to study the removal of sulfur dioxide (SO
2) from the flue gas. The results showed that the water-bath ...microwave method has some advantages of short reaction time and good yields. The synthesis of ethanolamine lactate ILs was fundamentally studied by an orthogonal experiment design (L
9(3
4)). Based on statistic analysis, it is revealed that the molar ratio of ammonium/acid is the most significant variable, and the optimized preparation conditions are under 338
K, wave power of 300
W for 30
min with the molar ratio 1:1.1 (ethanolamine vs. lactic acid). At the same condition, the yield of the other ILs was over 90% except dimethyl ethanolamine-based ILs. Results showed that the solubility of SO
2 in ethanolamine lactate ILs was 0.51 (mole fraction), higher than others. Ethanolamine lactate ILs was a better absorbent for SO
2. The optimal temperature for the absorption and desorption process were 298 and 363
K, respectively. The optimal desorption time was 60
min. It was also found that water-bath microwave can improve the release of the absorbed SO
2 from ILs.
The integration of a microbial electrolysis cell (MEC) is an effective strategy for enhancing the efficiency and stability of an anaerobic digestion (AD) system for energy recovery from ...waste-activated sludge (WAS). Typically, electrodes are arranged as separate components, potentially disrupting mixing and complicating the reactor configuration, posing challenges for the scaling up of AD-MEC coupling systems. In this study, electrodes were introduced into a continuous stirring tank reactor (CSTR) in a “stealth” manner by integrating them with the inner wall and stirring paddle. This electrode arrangement approach was validated through a sequential batch digestion experiment, resulting in a remarkable 1.5-fold increase in cumulative methane production and a shortened lag period compared to the traditional CSTR with a nonconductive inner wall and stirring paddle. Both the conductive materials (CMs) employed in the electrodes and the electrochemical processes equally contributed to the observed enhancement effect of the electrodes by regulating the evolution of the microbial community within the electrode biofilms, with a specific emphasis on the enrichment of methanogens (primarily Methanobacterium). This research offers a potential avenue to solve the contradiction between the electrode introduction and the mixing operation in AD-MEC coupling systems and to contribute to its future commercial application.
Membrane technology has aroused great attention for gas separations due to its high energy efficiency, small capital investment, easy and continuous operation. Mixed matrix membranes (MMMs) ...constructed from a continuous polymer phase and a dispersed filler phase offer new opportunities to achieve a breakthrough in fabricating high-performance membranes. Metal–organic frameworks (MOFs) have been regarded as potential fillers to boost the MMM separation performance. However, MOFs occasionally exhibit limited compatibility with the polymer matrixes owing to their partially inorganic structure and tendency of agglomeration in the membranes. Here, an interfacial design strategy is demonstrated by coating size-selective MOF cores with covalent organic framework (COF) layers to construct MOF@COF hybrids as fillers in MMMs for enhanced polymer-filler compatibility. The pure organic COF layers exhibit high affinity to the polymer matrix, thereby preventing the formation of nonselective interfacial voids and alleviating filler agglomeration. With the incorporation of only 5 wt% of MOF@COF fillers, the resultant MMM exhibits 48% and 79% enhancements in CO2 permeability and CO2/CH4 selectivity, respectively, with better operational stability compared to that of the pure polymeric membrane. These results reveal a novel filler design strategy for the tailored synthesis of high-performance MMMs for natural gas and biogas purification.
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•A novel MOF@COF hybrid was successfully prepared and explored as a promising membrane filler in polysulfone matrix.•The COF coating layer can largely improve the polymer-filler interfacial compatibility in MOF@COF-based MMMs.•A simultaneous increase in CO2 permeability and CO2/CH4 selectivity has been achieved in MOF@COF-based MMMs.
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•A series of heteroatom-doped porous carbon nanosheets are developed.•A maximum 244% increase in BET specific surface area is realized.•The molten salt-confined pyrolysis synthesis ...has a great universality.•Outstanding specific capacitance and energy density have been achieved.
Carbon nanosheets with heteroatom doping and well-developed porosity exhibit broad application foreground for Zn-ion hybrid supercapacitors (ZHSCs), but the simple and controllable preparation is still of great challenge. In this study, by using LiCl-KCl as in-built templates, histidine as carbon and nitrogen sources, and KNO3, K2SO4, KOH or Na2S2O3 as active agent, a series of N and NS doped porous carbon nanosheets are developed. Results indicate that, with the activator introduction, pore structures of the carbonized products are notably boosted, showing an astounding 30–244 % increase in BET specific surface area, and meanwhile, heteroatom with a content of ca. 12 % can be doped into the resultant carbon skeletons. Specifically, the NSPCN-800 (activated by Na2S2O3) with a large specific surface area of 1297 m2/g, a hierarchically porous structure composed of abundant micropores and mesopores, and a suitable heteroatom content (N: 11.9 wt%; S: 0.6 wt%) presents an impressive energy storage behavior as cathode for ZHSCs, including a specific capacitance of 165.8F/g, a specific capacity of 95.2 mAh/g, an energy density of 59.0 Wh kg−1 and a cyclic stability with a 82.6 % capacity retention after 5000 cycles. These performance parameters surpass numerous reported ZHSCs, making NSPCN-800 a very promising cathode for practical use.
•A novel bifunctional nanocomposite based on Fe3O4@SiO2-NH2 and Carbon quantum dots was designed.•The nanocomposite can be used for the detection of Cu2+ via fluorescence quenching mechanism.•The ...detection limit for fluorescent sensing of Cu2+ in water was 0.16 μM.
A new type of magnetic fluorescent nanocomposite (Fe3O4@SiO2-NH2/CQDs) was prepared by bonding carbon quantum dots (CQDs) with Fe3O4@SiO2-NH2 nanocomposites through amine-carbonyl interactions. The results showed that the prepared nanocomposites have spherical structure with good dispersion in aqueous solution, superparamagnetic and good fluorescence properties. In addition, the Fe3O4@SiO2-NH2/CQDs nanocomposites were used as a fluorescent probe for the first time to detect Cu2+, and exhibited high sensitive and selective detection properties in a wide linear range of 0–80 μM. The limit of detection (LOD) for Cu2+ was 0.16 μM.
Mixed matrix membranes (MMMs) have long been considered as promising membrane types for industrial energy-intensive gas separation processes. Current MMMs are still facing grand challenges of poor ...filler dispersion and poor polymer-filler interfacial compatibility. The present study demonstrates that these challenges can be addressed by fabricating MMMs containing three-dimensional (3D) covalent organic framework (COF) fillers with ultrasmall size-selective pores. Two different polymer matrixes, including glassy 6FDA-DAM and rubbery Pebax, are explored to validate the effectiveness of 3D COF fillers in improving the membrane separation performance. The pure organic nature of COFs facilitates their high affinity with pure organic polymer matrixes, leading to good interfacial compatibility in the resultant MMMs. These porous COF-300 fillers can increase the membrane fractional free volume that enhances the membrane gas permeability. Besides, the ultrasmall pores of COF-300 fillers and the rigidified polymer chains at the filler surface can enhance the size discriminative processes, resulting in increased membrane gas pair selectivity. Moreover, the separation performance of COF-300 can be further improved by functionalizing it with polyethylenimine (PEI), enabling the design of advanced membranes suitable for industrial applications.
