Hypercrosslinked Ionic Polymers with High Ionic Content for Efficient Conversion of Carbon Dioxide into Cyclic Carbonates

The effective conversion of carbon dioxide (CO2) into cyclic carbonates requires porous materials with high ionic content and large specific surface area. Herein, we developed a new systematic post-synthetic modification strategy for synthesizing imidazolium-based hypercrosslinked ionic polymers (HIPs) with high ionic content (up to 2.1 mmol g−1) and large specific surface area (385 m2 g−1) from porous hypercrosslinked polymers (HCPs) through addition reaction and quaternization. The obtained HIPs were efficient in CO2 capture and conversion. Under the synergistic effect of high ionic content, large specific surface area, and plentiful micro/mesoporosity, the metal-free catalyst [HCP-CH2-Im][Cl]-1 exhibited quantitative selectivities, high catalytic yields, and good substrate compatibility for the conversion of CO2 into cyclic carbonates at atmospheric pressure (0.1 MPa) in a shorter reaction time in the absence of cocatalysts, solvents, and additives. High catalytic yields (styrene oxide, 120 °C, 8 h, 94% yield; 100 °C, 20 h, 93% yield) can be achieved by appropriately extending the reaction times at low temperature, and the reaction times are shorter than other porous materials under the same conditions. This work provides a new strategy for synthesizing an efficient metal-free heterogeneous catalyst with high ionic content and a large specific surface area from HCPs for the conversion of CO2 into cyclic carbonates. It also demonstrates that the ionic content and specific surface area must be coordinated to obtain high catalytic activity for CO2 cycloaddition reaction

3D-Nanosponge enabled segregation: a versatile approach for highly dispersed and high content functionalization of metal oxide species

Nanomaterials functionalized with metal oxide species have aroused broad research interest in biomedical, catalysis and adsorption applications. However, a generalized functionalization approach achieving both high dispersity and high content of metal oxide species is rarely reported. In this study, a novel three-dimensional nanosponge (3D-NS) enabled strategy is developed to tackle this challenge. Instead of directly modifying metal species onto nanoparticles as performed in conventional approaches, the “empty” pores of nanoparticles are creatively converted into a “sponge-like” 3D nanospace by filling up with resoles rich in metal anchors, which efficiently accommodate high content metal species and maintain their highly dispersed state during the fabrication process. This strategy is generic to achieve highly dispersed metal functionalization of different single and binary metal compositions. As a demonstration, highly dispersed copper species derived from this strategy show excellent Fenton-like catalytic activity and enhanced cancer cell inhibition performance. These findings provide new understanding and useful tools for the development of metal functionalized nanomaterials for advanced applications

Molecular Dynamics Simulations of the Short-Chain Fluorocarbon Surfactant PFH_XA and the Anionic Surfactant SDS at the Air/Water Interface

The research and development of alternatives to long-chain fluorocarbon surfactants are desperately needed because they are extremely toxic, difficult to break down, seriously harm the environment, and limit the use of conventional aqueous film-forming foam fire extinguishing agents. In this study, mixed surfactant systems containing the short-chain fluorocarbon surfactant perfluorohexanoic acid (PFHXA) and the hydrocarbon surfactant sodium dodecyl sulfate (SDS) were investigated by molecular dynamics simulation to investigate the microscopic properties at the air/water interface at different molar ratios. Some representative parameters, such as surface tension, degree of order, density distribution, radial distribution function, number of hydrogen bonds, and solvent-accessible surface area, were calculated. Molecular dynamics simulations show that compared with a single type of surfactant, mixtures of surfactants provide superior performance in improving the interfacial properties of the gas–liquid interface. A dense monolayer film is formed by the strong synergistic impact of the two surfactants. Compared to the pure SDS system, the addition of PFHXA caused SDS to be more vertically oriented at the air/water interface with a reduced tilt angle, and a more ordered structure of the mixed surfactants was observed. Hydrogen bonding between SDS headgroups and water molecules is enhanced with the increasing PFHXA. The surface activity is arranged in the following order: PFHXA/SDS = 1:1 > PFHXA/SDS = 3:1 > PFHXA/SDS = 1:3. These results indicate that a degree of synergistic relationship exists between PFHXA and SDS at the air/water interface

Fractal-in-a-sphere: confined self-assembly of fractal silica nanoparticles

Fractal objects such as snowflakes and trees are ubiquitous in nature. However, fractal nanoparticles with uniform morphology and controllable structures are difficult to make. Herein, using a fractal-in-a-sphere strategy, we report the confined self-assembly of fractal silica nanoparticles with tunable fractal generations and uniform sizes. One advantage of controllable fractal generations has been demonstrated in enzyme delivery for parasite oocyst control. The fractal silica nanoparticles exhibited better oocysticidal performance compared with nanoparticles of other structures due to combined effects of enhanced adhesion, penetration across the oocyst wall, and high local enzyme concentrations. This study paves the way for the fabrication of fractal silica nanoparticles with fine structures and versatile applications

Synthesis of Carboxyl Modified Polyether Polysiloxane Surfactant for the Biodegradable Foam Fire Extinguishing Agents

It is necessary to develop novel and efficient alternatives to fluorocarbon surfactant and prepare fluorine-free environmentally-friendly fire extinguishing agent. The carboxyl modified polyether polysiloxane surfactant (CMPS) with high surface activity was synthesized via the esterification reaction using hydroxyl-containing polyether modified polysiloxane (HPMS) and maleic anhydride (MA) as raw materials. The process conditions of the esterification reaction were optimized by orthogonal tests, and the optimum process parameters were determined as follows: reaction temperature of 85 °C, reaction time of 4.5 h, isopropyl alcohol content of 20% and the molar ratio of HPMS/MA of 1/1. The chemical structure, surface activity, aggregation behavior, foam properties, wetting properties and electron distribution were systematically investigated. It was found that the carboxyl group was successfully grafted into silicone molecule, and the conjugated system was formed, which changed the interaction force between the molecules and would affect the surface activity of the aqueous solution. The CMPS exhibited excellent surface activity and could effectively reduce the water’s surface tension to 18.46 mN/m. The CMPS formed spherical aggregates in aqueous solution, and the contact angle value of CMPS is 15.56°, illustrating that CMPS had excellent hydrophilicity and wetting performance. The CMPS can enhance the foam property and has good stability. The electron distribution results indicate that the introduced carboxyl groups are more inclined towards the negative charge band, which would be conducive to weak the interaction between molecules and improve the surface activity of the solution. Consequently, new foam fire extinguishing agents were prepared by using CMPS as a key component and they exhibited excellent fire-fighting performance. The prepared CMPS would be the optimal alternative to fluorocarbon surfactant and could be applied in foam extinguishing agents