ABSTRACT
Polypropylene has been used for applications requiring high mechanical properties, good adhesion, chemical stability and insulation. Whereas, Polypropylene itself is flammable, and its limiting oxygen index (LOI) is low, which cannot pass the UL-94 combustion test. Therefore, extensive use will cause a serious threat to human life and property. With the wide application of thermoplastic polypropylene in industry, the development of environmentally friendly flame retardant materials has become an important research direction. For the past dozen years, researchers have been exploring flame retardants with high flame retardant efficiency, low toxicity, less smoke or other excellent performance flame retardants. This paper reviews the research progress of some phosphorus-containing flame retardants on the flame retardant properties of polypropylene in recent years. Phosphorus flame retardant is a flame retardant with high flame retardant efficiency, good stability and wide application. The types and flame retardant properties of phosphorus flame retardant will be introduced, and the future research of phosphorus flame retardant is summarized, direction and development opportunities.
ABSTRACT
Co3O4 nanostructures have been extensively studied as anode materials for rechargeable lithium-ion batteries (LIBs) because of their stability and high energy density. However, several drawbacks including low electrical transport and severe volume changes over a long period of operation have limited their utilities in LIBs. Rational composite design is becoming an attractive strategy to improve the performance and stability of potential lithium-ion-battery anode materials. Here, a simple method for synthesizing hollow Co3O4@TiO2 nanostructures using metal-organic frameworks as sacrificial templates is reported. Being used as an anode material for LIBs, the resulting composite exhibits remarkable cycling performance (1057 mAh g-1 at 100 mA g-1 after 100 cycles) and good rate performance. The optimized amorphous Co3O4@TiO2 hollow dodecahedron shows a significant improvement in electrochemical performance and shows a wide prospect as an advanced anode material for LIBs in the future.
ABSTRACT
Isostructural zirconium-based metalâ»organic frameworks (Zr-MOFs) have attracted the attention of researchers because of their remarkable stability at high temperatures and high pressures and their chemical stabilities against acids and bases. Due to this stability, Zr-MOFs can be utilized in adsorption research, and the adsorption performance of a Zr-MOF depends on the pore size and the surroundings of the MOF. In this study, as the dimensions changed and the adsorption was carried out, the Zr-MOF material remained stable, and the adsorption of the best state was achieved at 235 mg/g. Through the simulation of theoretical kinetic models of Zr-MOFs, we initially postulated that the adsorption capacity is proportional to the pore size and that acid orange 7 (AO7) was adsorbed by the MOFs. Afterwards, we verified our hypotheses through a series of Brunauerâ»Emmettâ»Teller (BET) data analysis; non-local density function theory (NLDFT) was mainly used to analyze the data. Moreover, we determined that physical adsorption occurs on the surface of the MOFs during the adsorption process, while chemisorption occurs in the form of dye molecules combining with active sites. Ultimately, we concluded that the larger the pore size, the stronger the adsorption capacity, and this contribution casts a new light on the issue of wastewater treatment.
ABSTRACT
Zirconium based metal organic frameworks (Zr-MOFs) have become popular in engineering studies due to their high mechanical stability, thermostability and chemical stability. In our work, by using a theoretical kinetic adsorption isotherm, we can exert MOFs to an acid dye adsorption process, experimentally exploring the adsorption of MOFs, their external behavior and internal mechanism. The results indicate their spontaneous and endothermic nature, and the maximum adsorption capacity of this material for acid orange 7 (AO7) could be up to 358 mg·g-1 at 318 K, estimated by the Langmuir isotherm model. This is ascribed to the presence of an open active metal site that significantly intensified the adsorption, by majorly increasing the interaction strength with the adsorbates. Additionally, the enhanced π delocalization and suitable pore size of UiO-66 gave rise to the highest host-guest interaction, which further improves both the adsorption capacity and separation selectivity at low concentrations. Furthermore, the stability of UiO-66 was actually verified for the first time, through comparing the structure of the samples before and after adsorption mainly by Powder X-ray diffraction and thermal gravimetric analysis.
