Synthesis Of Ordered Mesoporous Carbons By Two-Step Method In Aqueous Solution

Ordered mesoporous carbons (OMCs) can be extensively applied in many fields, such as electrochemical double-layer capacitors (EDLC), semiconductors, separation, adsorption, gas storage, and catalysts supports. They have been attracted much attention due to their excellent physical and chemical properties, including their high surface area, large pore volume, uniform and designable pore size, good thermal and electric conductivity, superior thermal and hydrothermal stability, quite chemically stable under nonoxidizing conditions and low cost of manufacture. In this dissertation, we demonstrate an efficient synthesis of highly ordered mesoporous carbon through a "two-step" strategy in acidic aqueous solution, by using phenol/formaldehyde resin as carbon precursor and commercial triblock copolymer pluronic F127as template. The mesophase was formed through the self assembly of phenolic resol and F127, with the controlled polymerization rate of phenolic resol around the micelles of F127.The main contents are as follows:(1) A "two-step" strategy was presented to synthesize highly ordered hexagonal mesoporous carbons under aqueous conditions. The whole synthesis process can be completed within1-6hours, and carried out under relative wider synthesis conditions, which make the "two-step" strategy an efficient way. The carbonization temperature, acid concentration and also the resol/F127mass ratio have great effect on the structural properties of OMCs. The synthesized samples were then sulfonated in concentrated sulfonic acid to prepare SOsH-modified OMCs. The combination of pyrolysis and sulfonation temperature is essential for developing OMCs with high densities of SO3H groups.(2) The anions eounterion of the acid has a great effect on the structural properties of the synthesized OMCs. Due to the nonvolatile H3PO4, plenty of P-containing groups can be introduced into the carbon framework after the carbonization process, which lead to the higher anti-oxidation properties of the sample during the oxidation process in acidic (NH/O2S2O8. It is worth to noting that the P-containing groups can be as active adsorption sites for heavy metal ions Co2+, and is favorable to enhance the adsorptive capacity of Co2+. After oxidation treatment, the P-incorporated sample has a high adsorptive capacity of69.3mg/gforCo2+(3) We developed a Zr-assisted hydrothermal synthesis of OMCs with hierarchical structure properties. In the acidic solution, the species are present in the form of zirconium polyoxo oligomers, which can interact with the resol and the PEO group of F127by hydrogen-bonding. So, under the assistance of zirconium polyoxo oligomers, the polymerization of resol can be controlled at a moderate rate around the micelles of F127, and the volume ratio of PEO to PPO group of F127can also be increased under hydrothermal conditions, which lead to the formation of the body-centered cubic mesostructure. After activated by KOH, the microporous fraction of the synthesized sample increased obviously, especially for the ultra-microporous fraction (pore size smaller than0.8nm), which is favorable for enhancing the adsorption capacity of the sample for CO2and CH4(25℃and1atm, up to4.1and1.9mmol/g, respectively). As the support for Fe catalyst, the hierarchical carbons show an outstanding performance in the hydrogenation of CO2into hydrocarbons, compared with that of SiO2, Al2O3and activated carbon.(4) By using H3PO4as catalyst, OMCs with high surface area, large pore volume and high phosphorus content, were synthesized through careful control of the H3PO4concentration. The P-containing groups on the surface of OMCs are mainly in the form of acid phosphate (C-O-PO3), which is favorable to enhance the anti-oxidation property of the samples and the adsorption capacity of methylene blue.