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Fixing the greenhouse gas CO2 through epoxide helps to mitigate worldwide ecological troubles. The applications of metal‐free and solvent‐free catalysts remain a challenge for CO2 catalytic conversion. In this work, an array of quaternary ammonium salts derived from polyethyleneimine with hydroxyl groups ([PEI‐GDMAB‐Cn]Br) were constructed by the reaction of branched PEI with a molecular weight of 10000 and glycidyl alkyl dimethylammonium bromide. A range of experiments were designed to demonstrate that [PEI‐GDMAB‐Cn]Br can be considered as a valid metal‐free and solvent‐free homogeneous catalyst for the CO2‐epoxide cycloaddition reaction. Among of [PEI‐GDMAB‐Cn]Br, [PEI‐GDMAB‐C18]Br catalyzed the model reaction of CO2 and epichlorohydrin under optimized reaction conditions (T=80 °C, 1.0 atm CO2, catalyst 1 mol%, ECH 15 mmol, 16 h) and the conversion achieved at 97.5 %. Moreover, the catalyst exhibited stable reusability and broad substrate applicability, which was used in the following cycle succinctly, because of self‐separated properties by temperature control. The [PEI‐GDMAB‐C18]Br catalyzed reaction process was detected as a pseudo‐first‐order reaction after kinetic studies and an Ea was calculated to be 50.65 kJ/mol. A combinatorial catalytic mechanism of hydrogen bonding and bromide ions is suggested to explain the remarkable catalytic performance of this bifunctional catalyst. [ABSTRACT FROM AUTHOR]

We prepared two types of multidimensional gradient hydrogels by simple electrophoresis using spherical graphite electrode. To explore their application in controlled drug release, rhodamine B (RB) and sodium salicylate (SS) were used as oppositely charged drug models respectively to in situ loading into the hydrogels by electrostatic interaction with the charged components accordingly. In both cases, the model drugs and the charged components of the hydrogels were gradiently distributed with the drug concentration increased from the gel surface to the gel core. For the crosslinking gradient hydrogel prepared at 2 V, the network size near the gel surface is about 3 times that of the gel core, and the release rate is 0.85 times of that of the non-gradient hydrogel. For the polymer chain gradient hydrogel prepared at 2.5 V, the relative content of polymer chain near the core of the gel is 2.5 times that of the gel surface, and the release rate is 0.71 times of the non-gradient hydrogel. [ABSTRACT FROM AUTHOR]

Nitrogen oxides (NOx) pollutants can cause a series of environmental issues, such as acid rain, ground-level ozone pollution, photochemical smog and global warming. Photocatalysis is supposed to be a promising technology to solve NOx pollution. Graphitic carbon nitride (g-C3N4) as a metal-free photocatalyst has attracted much attention since 2009. However, the pristine g-C3N4 suffers from poor response to visible light, rapid charge carrier recombination, small specific surface areas and few active sites, which results in deficient solar light efficiency and unsatisfactory photocatalytic performance. In this review, we summarize and highlight the recent advances in g-C3N4-based photocatalysts for photocatalytic NOx removal. Firstly, we attempt to elucidate the mechanism of the photocatalytic NOx removal process and introduce the metal-free g-C3N4 photocatalyst. Then, different kinds of modification strategies to enhance the photocatalytic NOx removal performance of g-C3N4-based photocatalysts are summarized and discussed in detail. Finally, we propose the significant challenges and future research topics on g-C3N4-based photocatalysts for photocatalytic NOx removal, which should be further investigated and resolved in this interesting research field. [ABSTRACT FROM AUTHOR]

[Display omitted] • Mesoporous polymer ionic liquids for the immobilization of lipase demonstrated mesoporous properties. • Resultant systems were used as recyclable biocatalysts for ester production. • Lipase immobilization led to higher stability than that of the free enzyme. • The process can generate high-purity esters using lipase-immobilized mesoporous polymer ionic liquid. Herein, fatty acid esters were synthesized cost-effectively from various fatty acids using reusable lipase (L) immobilized with novel porous ionic polymer (PIP) (l –PIP). The functionalized mesoporous PIP was synthesized through Friedel–Crafts alkylation reaction of 1, 4-bis(bromomethyl) benzene in the presence of ferric chloride as catalyst, and lipase was completely immobilized with PIP at varied time, forming l –PIP–6 H , l –PIP–12 H , l –PIP–18 H , l –PIP–24 H , l –PIP–30 H , and l –PIP–36 H , which were applied in ester production. l –PIP–30 H was characterized using FT–IR, SEM, XPS, solid–state 13C NMR, and N 2 adsorption–desorption isotherms. The conversion of oleic acid reached 88.21 % under optimized conditions (12:1 ethanol/oleic acid molar ratio after 5 h at 45 °C with 250 wt% catalyst at 300 rpm). The stability and reusability of l –PIP–30 H were demonstrated by the sustained catalytic efficiency for at least six reaction cycles. Good catalytic activity during the esterification of various free fatty acids with ethanol was observed. This cost–efficient and effective lipase–immobilized PIP catalyst may have positive economic and environmental repercussions to inspire further academic and industrial research on biodiesel. [ABSTRACT FROM AUTHOR]

Building the differential growth through the thickness is a promising and challenging approach to design the morphing structures of hydrogel actuators. Besides retaining the size of the hydrogel actuators under environmental stimuli still remains a big challenge. Herein, a facile and universal approach is developed to address both issues by introducing PEG during the polymerization of N‐isopropylacrylamide (NIPAm) via one step method using asymmetric mold. Both composition gradient and pore gradient are obtained in micro level along the thickness direction of the final hydrogel, while thin‐thickness gradient in macro level. The thickness gradient and water retention can be controllably adjusted by changing PEG concentration. The introduction of PEG effectively improves both responsive and non‐shrunken performance by the interaction with PNIPAm. The resultant anisotropic PNIPAm/PEG hydrogel respond quickly and reach maximum deformation (360°) within 10 s at low temperature (40 °C). The various 3D shape and biomimetic movement can be programmed by simply controlling the PEG concentration and mold shape. This strategy can provide new insights into the design intelligent soft materials with 3D morphing for bioinspired and biomedical applications. [ABSTRACT FROM AUTHOR]

• Co-Salen complexes containing different groups and bearing potassium iodide (KI) complexed with crown ether (K@SCs) were prepared. • Salen derivative organic polymer as heterogeneous catalyst for CO 2 cycloaddition reaction. • Alkali metal halides and Lewis acids have good synergistic effects in catalytic reactions. Metallosalen presents very important applications in both homogenous and heterogeneous catalysis. Correspondingly, porous polymeric metallosalen combined with the performance of organometallics and heterogeneous polymers possess potential in CO 2 fixation reactions. Herein, a family collection of K@SCs were conceived and obtained by combining cobalt-salen complexes with different groups and diaminobenzene-18-crown-6 complexed with KI, which allows multiphase catalytic immobilization of CO 2 to epoxides. Catalyst K@SC-3 can fix CO 2 into a variety of substituted epoxides in >90% yields to the corresponding cyclic carbonates in co-catalyst-free and solvent-free conditions. Furthermore, K@SC-3 can be recovered and reused at least six times by simple centrifugal separation, demonstrating superior stability. The kinetics experiments were also carried out at varied temperatures catalyzed by K@SC-3. It is concluded that a first-order equation of epoxide was proved and the activation energy was calculated to be 27.13 KJ/mol. [Display omitted] [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Dual NC hydrogel with homogeneous SiO 2 @TiO 2 core-shell nanoparticle was fabricated. • Interaction of SiO 2 @TiO 2 NPs and polymers enhanced fluorescent stability. • Fluorescence and toughness were adjusted by the shell thickness of SiO 2 @TiO 2 NPs. • Dual crosslinking and dual nanocomposite contributed to high mechanical property. Abstract A tough and fluorescent NC hydrogel was fabricated by introduction of SiO 2 @TiO 2 core-shell structure nanoparticles (NPs) into polyacrylamide (PAAm)/Laponite nanocomposite (NC) hydrogel. The photoluminescent and mechanical properties of the resultant PAAm/Laponite/SiO 2 @TiO 2 dual NC hydrogel were explored with respect to the shell thickness of SiO 2 @TiO 2. The dual NC hydrogel emitted stable and bright blue photoluminescence (PL), when radiated at 350 nm. The emission wavelength was slightly shifted from 423 to 428 nm with the increasing of the shell thickness due to the surface interaction of SiO 2 @TiO 2 NPs and polymers. Besides, the compressive strength and compressive fracture energy of the PAAm/Laponite/SiO 2 @TiO 2 dual NC hydrogels were 7535.8 kPa and 5740.3 J/m2 which increased by 19 and 21%, respectively, relative to the MLS@T 0 dual NC hydrogel. The tensile strength was 207.2 kPa at a strain of 730%. The dual crosslinking of SiO 2 @TiO 2 NPs and Laponite, as well as the dual nanocomposite structure were responsible for the enhanced mechanical properties. [ABSTRACT FROM AUTHOR]

• The Tröger base analogue coordinated with potassium iodide and containing crown ether CATB-KI was fabricated. • The acidified CATB-KIs shown high catalytic efficiency to cyclic carbonates. • The synergistic mechanism has been proved in terms of experimental results and calculation of dynamics. Tröger's bases (TB) containing two steric nitrogen atoms, are alternated as building block for constructing molecular acceptors to form covalent bonds with acids, making TB a promising catalyst. Herein, TB analogs fabricated with crown ethers were knitted by condensation reaction and combined with potassium iodide as a brand-new catalytic system (CATB-KIs), which were characterized using FT-IR, 13C CP MAS NMR, SEM, TGA, and XPS spectroscopy respectively. The generated CATB-KIs exhibited excellent performance for CO 2 fixation reaction with epoxides to produce cyclic carbonates under mild conditions, and the catalytic activity could be further improved by coordinating with acids beforehand, in which HBr performs fascinated activity. After 12 h, the corresponding cyclic carbonate from epichlorohydrin with 95.1% yield was detected at mild conditions with solvent-free in the presence of CATB-KI-2 and HBr. A series of terminal epoxides were converted into desired cyclic carbonates with desirable yields. The catalyst could be recovered successfully and reused six times without significant loss of activity. Finally, dynamics study on catalytic mechanism has been accomplished and the activated energy was calculated as 72.1 kJ/mol. A synergistic catalytic mechanism of hydrogen bonding and I anion has been proposed to account for the excellent catalytic activity of this catalysts. [Display omitted] [ABSTRACT FROM AUTHOR]

• Hydrogel-born foam is successfully fabricated by simple microwave-induced foaming. • The conversion of amide to imide can tune the hydrophilic/hydrophobicity of the foam. • The foam shows excellent mechanical, thermal insulation and fire-retarding properties. Hydrogel-born foam materials have been intensively developed because of great potential in various fields and environmental friendliness with water as foaming agent. However, the energy-consuming nature and pore collapse in the preparing and using process limit their application. Herein, a facile strategy is present to fabricate a dimensional stable hydrogel-born foam by simple acid-heat treatment and subsequent fast microwave foaming. The microwave heating rapidly evaporates and expands water into cells in the gel while the heat softening of the hydrogel further facilitates the formation of the cells. Moreover, the hydrophilicity/hydrophobicity and the crosslinking degree of the foam can be regulated by controllable conversion of amide groups of the hydrogel to the imide groups during the acid-heat treatment. As a result, it successfully avoids the pore collapse in both of the preparation and use process. With hierarchical pore structure and controllable moisture absorption, the foam shows with excellent dimensional and thermal insulation. In addition, the foam provides superior mechanical properties and fire retardance over traditional foams. The flame-retardant mechanism was proposed. The fabrication of this hydrogel-born foam is facile, flexible and can be adapted for extensive applications in building structures. [ABSTRACT FROM AUTHOR]