Application Of Nano Porous Materials In The Phase Change Energy Storage And Catalytic Oxidation Reaction

Nano-porous materials which combine the size effect of nanomaterials and pore characteristics of porous materials have received extensive attention in the field of scientific research and practical applications. Especially, the building of new composite materials guided by the functional regulation of nano-porous materials to achieve functional integration is the research hotspot and difficulty in the today’s field of nanotechnology.In this paper, mesoporous silica molecular sieve, metal-organic framework materials and porous transition metal oxide were chosen as the research objects, the functional assembly technique to customize the function-oriented composite materials was developed. The impact of surface properties, pore microenvironment and active components of porous materials on the phase change energy storage and catalytic properties was investigated in detail. The above studies will provide theoretical and experimental foundation for the structural design, performance control and practical application of the nano-porous materials. The detailed works are sumerized as follows:(1) The regulation of channel surface properties of silica molecular sieve to achieve the phase change energy storage of PEG:When PEG was stabilized in mesoporous SBA-15 with hexagonally ordered pore structures, phase change latent heat of this composite was disappeared. In this part, different kinds of functional terminal groups, such as-NH2 and-CH3. were respectively grafted on the internal/external surface of SBA-15 by the surface functionalization technique. Then, the influence of interface physical and chemical characteristics of the SAB-15 supports and PEG molecules on the phase change behavior and stability of PEG was explored. The amino groups modified on the internal surface of SBA-15 reduced the hydrogen bond interactions between PCM molecules and the channel surface of the supports, and also altered the adsorption conformation of the PEG chains from train structure to loop structure. The loop structure was conducive to the stretching and crystallization of the PEG chains. Further, the methyl groups grafted on the external surface of SBA-15 restrained the spillover of PEG molecules from the channels due to the opposite polarities of PEG molecules and methyl groups.(2) The regulation of pore microenvironment of metal-organic framework material to optimize its catalytic performance:Cr-MIL-101-NH2 with large pores. good thermal stability as well as excellent chemical stability to water and common organic solvents was chosen as candidate for post-synthetic modification. The pore microenvironment of the MOF support was regulated by varying the architecture of the Schiff base. The effect of pore microenvironment on the recycling stability and catalytic performance of the catalyst during the olefin epoxidation reaction was explored. In terms of the optimized catalyst, the Cr-MIL-101-NH2 MOF support with high surface area improved the dispersion of Co(II) ions. The uniform and big pores of the MOF guaranteed sufficient contact between the catalytic active sites and the substrate. The nitrogen atom in the pyridine ring as a strong electron-withdrawing substituent was conducive to electrophilic attack of the Co-peroxy species and then accelerated the rate of epoxidation. The strong coordination interaction between the Co(II) ions and chelating groups guaranteed the excellent recycling performance.(3) The mesoporous and ultrathin features of the transition metal oxide to improve its catalytic performance:Ultrathin mesoporous bimetallic oxide NiCo2O4 nanosheets with loose stacking structure have been prepared by a facile low temperature solution method followe by the pyrolysis. The NiCo2O4 nanosheets as efficient heterogeneous catalyst showed good catalytic activity and high selectivity during the oxidation of 4,4’-difluorodiphenylmethane into 4,4’-difluorobenzophenone. The ultrathin and mesoporous features with high specific surface area not only provided large amount of binary active sites of Co and Ni, but also improved the contacting ability between the substrate and these active sites. The mesoporous features of nanosheets offered appropriate channels for an efficient mass transfer of the catalytic reaction and accelerated the rate of reaction and provided high catalytic efficiency for benzylic oxidation.