其他摘要 | Microporous organic polymers (MOPs) can be defined as a series of porous materials with pore sizes smaller than 2 nm on average, which are comprised of light elements such as C, H, O, N, B and exhibit very high physical surface areas. To compare with inorganic pore materials the MOPs can be easily chemically modified the backbone of the bulk phase and show good performance in gas storage. Part I: a general over view of the microporous organic polymers.
Part II: Four carbazole-spacer-carbazole polymers PCz-Cn-Cz (n=3-6) with the similar topological model structures were designed and prepared by FeCl3 oxidative coupling polymerization. The Brunauer-Emmett-Teller (BET) specific surface areas of the obtained polymers are 862, 870, 768 and 785 m2 g-1, respectively, which are competitive with the reported conjugated microporous polymers. Interestingly, there are no obvious differences in the domain pore width (centred at 0.5 nm) and the pore size distribution among the four polymers, although they have different length soft alkylene chains to interlink same rigid backbone carbazole. This may be ascribed to the soft alkylene chains, which are easy to bend and result in intramolecular intercalation and pore filling. Gas (H2, CO2, CH4 and CO) adsorption isotherms show that the H2 storage of the polymers can be up to 1.33 wt% at 1.0 bar and 77 K, the uptake capacity for CO2 can reach 16.8 wt% at 1.0 bar and 273 K, the CH4 uptake can reach 2.11 wt% at 1.0 bar and 273 K and the CO uptake performance can be up to 1.37 wt% at 298 K and 1.0 bar. Selective adsorption of CO2/N2 and CO2/CH4 calculated using the initial gas uptake slopes shows that these networks display good selectivity with a maximum value of 47.7 (33.8) and 14 (7.3) at 273 K (298 K).Part III: Four covalent triazine-based frameworks (PCTF-1 to PCTF-4) were synthesized by a consolidated ionothermal reaction between aromatic nitriles under the catalysis of ZnCl2. The Brunauer-Emmett-Teller (BET) specific surface area values of PCTF-1 (853 m2 g-1), PCTF-2 (811 m2 g-1) and PCTF-3 (391 m2 g-1) are against with the increasing length of branched arm, indicating using monomers with longer branches are able to pack more efficiently, resulting in higher density materials with a lower surface area. PCTF-4, compared with PCTF-2, just changed the middle benzene of the branches to benzothiadiazole, however, N2 adsorption isotherms showed its BET specific surface area value (1404 m2 g-1) is the highest among the PCTFs, almost two times than that of PCTF-2. The nitrogen-rich characteristics of C3N3 triazine rings feature the frameworks strong affinity for CO2 and thereby high CO2 adsorption capacity. Especially for PCTF-4 with the benzothiadiazole, it exhibited the highest CO2 uptake (20.5 wt%) at 273 K and 1 bar, this value is one of the highest reported for covalent triazine-based frameworks. The results demonstrate that the introduction of strong polar groups (benzothiadiazole) into a polymer skeleton is an efficient strategy to produce CO2-philic microporous organic polymers with enhanced binding affinity with CO2 molecules. In addition, such PCTFs with high physical-chemical stability and comparable BET surface areas exhibited good ideal CO2/N2 selectivities (14-56) and CO2/CH4 selectivities (11-20) at 273 K, showing these materials are potential candidates for gas storage and separation. However, in the presence of water vapor, these performance of CO2 uptake all decreased due to via hydrogen bonding with water, suggesting materials that perform well in dry conditions may not always be the most promising materials under more practical conditions.
Part IV: the conclusion of the thesis. |
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