SYNTHESIS OF NITROGEN-RICH AND ULTRA- MICROPOROUS ORGANIC POLYMERS FOR SEPARATION OF CARBON DIOXIDE FROM GAS MIXTURES

摘要

Energy production and use account for two-thirds of the world's greenhouse-gas (GHG) emissions. At present, the vast majority of energy consumed by the human population is derived from burning fossil fuels because of their natural abundance and remarkably high energy density. This burning of carbon based fossil fuels not only gives off useful energy but also results in a chemical byproduct, CO2, which is a GHG and is considered a primary cause for global warming. In 2013, CO2 accounted for about 82% of all U.S. greenhouse gas emissions from human activities. At the Paris climate conference (COP21) in December 2015, 195 countries adopted the first-ever universal, legally binding global climate deal to control the emissions of CO2. Therefore, separation of CO2 from gas mixtures is an essential and important task for protecting our environment and generating economic benefits. Recently, porous solid materials have emerged as fascinating materials in gas storage and gas separation applications because of their high surface areas, low density, and particularly easy regeneration process. Among them, porous organic polymers pay significant attention because of their chemical and thermal stability as well as diverse synthetic routes to control the atomic heterogeneity though the reactions of varieties of functional groups. The presence of heteroatoms, particularly, the presence of nitrogen offers an important advantage by providing polar nature to the surface which is considered to affect the CO2 adsorption significantly. Tuning of pore size is another important tool to control the selective gas adsorption in an effort to separate the gas mixtures. It has been reported that smaller pores are more important than surface area in gas separation. However, controlling the pore sizes in subnanometer scale which is compatible with the sizes of small gas molecules is a big challenge. We report here the synthesis of a highly nitrogen-rich porous organic polymers by condensation reaction between ortho-diketone and ortho-diamine through phenazine-ring formation. Synthesized polymer possesses ultra-small pores in the range of 0.25-0.6 nm within the frame apertures, which significantly enhanced the CO2 sorption selectivity over methane (CH4) and nitrogen (N2).