| Large amount of CO2 emitting from the consumption of fossil fuels has led to the global climate change and some environmental issues. Therefore, CO2 capture and sequestration is essential for addressing these issues as the demand on fossil fuels continues to increase. Physisorption by porous solids is considered a promising strategy for CO2 capture, which offers possible energy saving compared with other well-established CO2 capture and sequestration technologies, such as liquid amine scrubbing technology that requires significant amounts of energy to recycle the liquid. Microporous organic polymers (MOPs), as a novel class of porous materials, have shown great potential for CO2 capture because of their low skeleton density, large specific surface area, narrow pore size distribution and high chemical stability. To this end, a wide variety of MOPs, including covalent organic frameworks (COFs), polymers of intrinsic microporosity (PIMs), conjugated microporous polymers (CMPs), hyper-crosslinked polymers (HCPs), porous aromatic frameworks (PAFs), and covalent triazine-based frameworks (CTFs), have been developed for CO2 capture. Most MOPs are synthesized by the well-established noble metal catalyzed polymerization reactions, in contrast, HCPs could be easily prepared by iron (III) chloride catalyzed Friedel-Crafts alkylation reaction, which avoids the use of precious metal coupling catalysts. Recent studies have revealed that the incorporation of electron-rich heteroatom into the skeleton of MOPs could enhance their binding affinity to CO2 molecules and thus their CO2 capture capacities. Based on this, a series of hyper-crosslinked polymers (HCPs) and carbon materials containing nitrogen atoms were synthesized so as to enhance the CO2 capture capacities:1. We designed and synthesized a monomer with triphenylamine unit by the Buchwald-Hartwing cross coupling reaction, and thus the triphenylamine-containing hypercrosslinked microporous organic polymers HTDTPP has been synthesized via one-step Friedel-Crafts alkylation reaction and formaldehyde dimethyl acetal promoted by anhydrous FeCb. This method is easy to operate and the reaction condition is mild. In addition, this method does not need a monomer with specific polymerisable groups. The catalyst is cheap and readily available thus lower reaction costs. The physical and chemical properties of the resulting oolvmer networks are stable. The apparent BET specific surface areas were found to be 1064 m2/g for HTDTPP. It exhibits a H2 uptake ability of 1.50 wt%(77 K/1.13 bar) with a CO2 uptake ability of 2.56 mmol/g at 273 K/1.13 bar, indicating that the microporous material has good gas adsorption properties. Then, we investigated the selectivity of the polymer networks and the calculated CO2/ CH4 and CO2/N2 adsorption selectivities were about 5.0 and 33.2 for HTDTPP at 273 K, respectively. Given the high surface area, the outstanding CO2 sorption performances, and the inexpensive reagents and catalyst employed, the polymer networks are promising candidates for CO2 capture and sequestration technology.2. We designed two pyrene-based building blocks with nitrogen atoms, and thus two novel pyrene-containing hypercrosslinked microporous organic polymers have been synthesized via one-step Friedel-Crafts alkylation reaction from these building blocks and formaldehyde dimethyl acetal promoted by anhydrous FeCl3. Furthermore, the gas adsorption performances have been investigated. The results prove that, HTPAPy, possessing higher micropore surface area and micropore volume, exhibits larger H2 uptake ability of 1.47 wt% and larger CO2 uptake ability of 3.22 mmol/g at 77 K/1.13 bar, since micropores mostly contribute to the H2 and CO2 adsorption. In addition, the nitrogen content of HTPAPy was also slightly higher than HDCZPy which has a certain contribution to improve the adsorption of carbon dioxide. The resulting polymers showed great potential in gas adsorption field, but the hypercrosslinked microporous organic polymers is difficult to control the pore size effectively, so the future direction is to achieve effective control of its pore size distribution.3. In order to further improve the adsorption properties of the polymers, we first prepared a nitrogen containing polymer as precursor, and then the precursor was directly carbonized at different temperatures mixed with potassium hydroxide to obtain a series of porous carbon materials. These carbon materials are advantageous in several ways, including a higher resistance to water, higher thermal, mechanical, and chemical stability, easy synthesis, tunable pore structure, higher specific surface areas and pore volumes, and, most importantly, low cost. The obtained carbon material HTPACz-K-700 exhibits the hightest H2 uptake ability of 2.94 wt%and the hightest CH4 uptake ability of 2.24 mmol/g with the apparent BET specific surface areas of 3363 m2/g. HTPACz-K-500 exhibits the hightest CO2 uptake ability of 6.6 mmol/g at 273 K/1.13 bar. Furthermore, the high selectivity of these carbon materials makes them promising material for CO2 separation. During the preparation of these carbon materials. potassium hydroxide plays a role in template to prevent the collapse of the pores in the porous organic polymers on the one hand, and on the other hand, it can produce new pore structure in the materials. |
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