Preparation Of Nitrogen - Rich Organic Microporous Polymer And Study On Its Gas Adsorption Performance

Microporous organic polymers (MOPs) show some advantages such as large specific surface area, high chemical and thermal stability, low skeleton density and synthetic strategy diversity. This could make MOPs strong candidates for gas capture and storage, separation of molecules and heterogeneous catalysis. MOPs could be divided into Polymers of Intrinsic Microporosity (PIMs), Conjugated Microporous Polymers (CMPs), Covalent Organic Frameworks (COFs) and Hypercrosslinked Microporous Polymer (HCPs) according to the different molecular structure. The introduction of polar functional groups (such as-NH2,-OH,-NO2,-COOH and -SO3H) into the solid adsorbents can leads to the increased gas (CO2, H2, CH4) sorption capacities, but the surface areas of the materials would be much lower because of the introduction of functional groups occupying some pores of the materials. In order to combine the high surface area with high CO2 capture capacity, we introducing nitrogen atoms into the skeleton of MOPs, which enhance the binding affinity between the materials and the CO2 molecules, and enhanced the CO2 sorption quantity. At the same time, the nitrogen atom is introduced into the polymer skeleton rather than as a side group, so the preparation of microporous organic polymers can be expected to show excellent surface area. Based on this, this master thesis synthesized nitrogen-rich heterocyclic CMPs, HCPs and carbon materials:1. Two novel monomers with the structural unit of triphenylamine has been designed and synthesized, and then the homocoupled and copolymer networks were synthesized via Yamamoto-type Ullmann cross-coupling reaction and Suzuki cross-coupling polycondensation. Through measured the porous properties and the gas uptake capacities of the polymers, the homocoupled polymer YPTPA catalyzed by Ni(cod)2 have a higher degree of crosslinking, and shows highly Brunauer-Emmet-Teller specific surface area up to 1557 m2/g with a high CO2 uptake ability of 3.03 mmol/g (1.13 bar/273 K) and CO2/N2 selective adsorption separation index is 17.3:1. The incorporation of nitrogen atoms into the skeleton of MOPs enhanced the binding affinity between the pore wall and the CO2 molecules, and then enchanced the adsorption quantity of CO2. Although the two polymers we synthesized have large surface area, high adsorption capacity and the structure is easy to controlled, the transition metal catalysts are used during the reaction process, so the production costs are relatively high.2. In order to synthesize porous organic polymers with lower cost and milder reaction conditions, our research focus on the HCPs. Two kinds of monomer with carbazole building blocks are synthesized, and the HCPs were synthesized by Friedel-Crafts alkylation reaction which used a formaldehyde dimethyl acetal (FDA) crosslinker and promoted by anhydrous FeCl3, this reaction is easy to operation and less by-products. Through the research of physical and chemical properties, we found that the FCTCz with a higher crosslinking degree shows highly specific surface area up to 1845 m2/g with a high CO2 uptake ability of 4.63 mmol/g (1.13 bar/273 K), and a high H2 uptake ability of 1.94 wt%(1.13 bar/77 K). Considering the high surface area, the outstanding CO2 sorption performances, and the facile preparation strategy, these polymer networks are promising materials for potential applications in post-combustion CO2 capture and separation. But it’s hard to achieve effective control for HCPs in pore size and distribution.3. In order to improve the performance of HCPs and get better gas adsorption ability, carbonized materials was obtained using the triphenylamine-based HCPs synthesized by Friedel-Crafts as the precursor and direct high-temperature treatment. The precursor carbonized with or without potassium hydroxide activation for testing the effect of activator. The carbonized materials with KOH show better performance than precursor, the activated carbon material of FCDTPA-K-700 exhibits a high surface area of 2065 m2/g and an exceptionally high CO2 uptake up to 6.51 mmol/g (1.13 bar/273 K), and with the H2 and CH4 uptake abilities of 2.61 wt%(1.13 bar/77.3 K) and 2.36 mmol/g (1.13 bar/273 K), respectively. This is mainly because KOH play a supportive role and can prevent the collapse of the pores in the porous organic polymer during carbonization with elevated temperature. On the other hand, KOH as a template agent can be produced new pore structure in the materials. So the gas adsorption ability of the materials can be improved in a large degree.4. A series of carbonized materials was obtained using the carzole-based HCPs mentioned before as the precursor by high-temperature treatment with KOH activation. The activated carbon material of FCBCz-600 show exceptionally high CO2 uptake up to 6.38 mmol/g (1.13 bar/273 K). The FCBCz-700 exhibit a high surface area of 2357 m2/g show the highest H2 and CH4 uptake abilities of 2.85 wt% and 2.39 mmol/g (273 K/1.13 bar), respectively. Besides KOH, carbonization temperature can also affect the properties of carbon materials. The carbonized materials obtained by high-temperature treatment have simply preparation method, high surface areas and the outstanding gas sorption performances, so it’s very promising for industrial applications such as post-combustion carbon dioxide capture and high-density clean energy storage, besides it provides a new way to produce carbon materials.