A novel and simple pathway to synthesis of porous polyurea absorbent and its tests on dye adsorption and desorption

A novel one-step protocol for the preparation of porous polyurea material (PPU) through precipitation polymerization of toluene diisocynate (TDI) is presented. The process is based on step polymerization of one singlemonomer, TDI, with water in water-acetonemixed solvent. PPU is obtained without need for any porogen or additives, and no any chemical modification on the outcome polymer is necessary. The morphology, pore size and size distribution of PPU are characterized by scanning electron microscope and BET nitrogen adsorption. Taking acid fuchsine (AF) and Congo Red as dye examples in wastewaters, their adsorption on, desorption from PPU and the reusability of PPU were tested. Experimental conditions for AF adsorption were optimized with regard to pH, adsorption time, AF concentration and amount of PPU. Results demonstrate that the as-prepared PPU is of high performance in dyes adsorption and recycled use. This work presents therefore a novel and attractive candidate for removal of anionic dyes from wastewaters.     

Optimal error estimates of a decoupled scheme based on two-grid finite element for mixed Stokes–Darcy model

Although the numerical results suggest the optimal convergence order of the two-grid finite element decoupled scheme for mixed Stokes–Darcy model with Beavers–Joseph–Saffman interface condition in literatures, the numerical analysis only gets the optimal error order for porous media flow and a non-optimal error order that is half order lower than the optimal one in fluid flow. The purpose of this paper is to fill in the gap between the numerical results and the theoretical analysis.     

Ni–Al composite hydroxides fabricated by cation–anion double hydrolysis method for high-performance supercapacitor

Chemical doping of nickel hydroxide with other cations(e.g. Al~(3+)) is an efficient way to enhance its electrochemical capacitive performances. Herein, a simple cation–anion(Ni~(2+)and AlO_2) double hydrolysis method was developed toward the synthesis of nickel–aluminum(Ni–Al) composite hydroxides. The obtained composite hydroxides possesses a porous structure, large surface area(121 m~2/g) and homogeneous element distribution. The electrochemical test shows that the obtained composite hydroxides exhibits a superior supercapacitive performances(specific capacitance of 1670F/g and rate capability of 87% from 0.5 A/g to 20 A/g) to doping-free nickel hydroxide(specific capacitance of 1227 F/g and rate capability of 47% from 0.5 A/g to 20 A/g). Moreover, the galvanostatic charge/discharge test displays that after 2000 cycles at large current density of 10 A/g, the composite hydroxides achieves a high capacitance retention of 98%, indicative of an excellent electrochemical cycleability.     

硅氧烷交联的咪唑基团功能化聚苯醚/聚四氟乙烯耐高温质子交换膜

以聚苯醚(PPO)为基体材料, 通过溴甲基化及咪唑基团功能化, 与聚四氟乙烯(PTFE)复合、 硅氧烷基团水解交联及磷酸掺杂, 制备了兼具高磷酸掺杂含量、 高质子电导率和良好机械性能的高温质子交换膜材料. 以甲基咪唑(MeIm)和咪唑基硅氧烷化合物(SiIm)为功能化试剂(其中咪唑基团提供了磷酸作用位点, 同时SiIm中的硅氧烷基团水解后得到Si—O—Si交联网络结构), 提高了膜材料的机械稳定性. 与PTFE的复合进一步增强了膜材料的机械强度. 结果表明, 复合膜具有较高的电导率和一定的机械强度. 当磷酸掺杂质量分数为242.5%时, PPO-50%SiIm-50%MeIm/PTFE复合膜在160 ℃不加湿条件下的电导率为0.09 S/cm, 室温下的断裂拉伸强度为3.6 MPa.     

One-pot Synthesis of a Truncated Cone-shaped Porphyrin Macrocycle and Its Self-assembly into Permanent Porous Material

Here, we report the synthesis of a truncated cone-shaped triangular porphyrinic macrocycle, P₃L₃ , via a single step imine condensation of a cis-diaminophenylporphyrin and a bent dialdehyde-based linker as building units. X-ray diffraction analysis reveals that the truncated cone-shaped P₃L₃ molecules are stacked on top of each other by π⋯π and CH⋯π interactions, to form 1.7 nm wide hollow columns in the solid state. The formation of the triangular macrocycle is corroborated by quantum chemical calculations. The permanent porosity of the P₃L₃ crystals is demonstrated by several gas sorption experiments and powder X-ray diffraction analysis.     

Highly N/O co-doped ultramicroporous carbons derived from nonporous metal-organic framework for high performance supercapacitors

A new nonporous Zn-based metal-organic framework (NPMOF) synthesized from a high nitrogen-containing rigid ligand was converted into porous carbon materials by direct carbonization without adding additional carbon sources. A series of NPMOF-derived porous carbons with very high N/O contents (24.1% for NPMOF-700, 20.2% for NPMOF-800, 15.1% for NPMOF-900) were prepared by adjusting the pyrolysis temperatures. The NPMOF-800 fabricated electrode exhibits a high capacitance of 220 F/g and extremely large surface area normalized capacitance of 57.7 μF/cm² compared to other reported MOF-derived porous carbon electrodes, which could be attributed to the abundant ultramicroporosity and high N/O co-doping. More importantly, symmetric supercapacitor assembled with the MOF-derived carbon manifests prominent stability, i.e., 99.1% capacitance retention after 10,000 cycles at 1.0 A/g. This simple preparation of MOF-derived porous carbon materials not only finds an application direction for a variety of porous or even nonporous MOFs, but also opens a way for the production of porous carbon materials for superior energy storage.     

Nanoporous silicon flakes as anode active material for lithium-ion batteries

Nanoporous-silicon (np-Si) flakes were prepared using a combination of an electrochemical etching process and an ultra-sonication treatment and the electrochemical properties were studied as an anode active material for rechargeable lithium-ion batteries (LIBs). This fabrication method is a simple, reproducible, and cost effective way to make high-performance Si-based anode active materials in LIBs. The anode based on np-Si flakes exhibited a higher performances (lower capacity fade rate, stability and excellent rate capability at high C-rate) than the anode based on Si nanowires. The excellent performance of the np-Si flake anode was attributed to the hollowness (nanoporous structure) of the anode active material, which allowed it to accommodate a large volume change during cycling.