Targeted Synthesis Of Porous Aromatic Frameworks For Gas Seprartion

Porous organic frameworks (POFs) have attracted enormous attention because of their tunablebuilding blocks, controlled pore connectivity and diverse functionalities. In this thesis, we chosesome specific gas separation system as the guidance, through effective monomer design, thechoice of polymerization and post-modification with different metal ions, targeted synthesis of aseries of new Porous Aromatic Frameworks. At the same time, by designing a new monomerreaction and choosing the novel catalyst, we present an economical approach to prepare porousorganic membrane, which can be used for gas separation. The main researches are listed asfollows:1. One of the most pressing environment concerns of our age is the escalating level of atmosphericgreenhouse gases, which is deemed as a significant contribution to global warming. The capture ofCO2and CH4carbon resources is also very important in energy conservation. In first part, we havesynthesized novel porous aromatic frameworks, PAF-18-OH and their lithiated derivative,PAF-18-OLi via a Sonogashira-Hagihara cross-coupling reaction. The tunability of the Li contentin PAF-18-OLi shows different capacities for CO2and H2adsorption. The completely lithiatedPAF-18-OLi exhibits the highest CO2and H2adsorption ability, which is due to strongerinteractions of gas molecules with the lithium derived PAF framework. CO2capture fromsimulated flue is exemplified by PAF-18-OH and PAF-18-OLi. In the case of PAF-18-OLi, highCO2/N2selectivity under ambient temperature and pressure is obtained, the value of which isalmost four times higher than that of PAF-18-OH at the same conditions. Notably, the PAF-18-OLimaterial also exhibits high stability. The development of high-performance lithiated porousorganic frameworks with remarkably high CO2/N2selectivity, excellent sorption capacity of CO2and H2, and high stability would pave the way for carbon dioxide capture and sequestration, andhydrogen storage.We have also successfully designed and synthesized a carboxyl-functionalized PAF material,PAF-26-COOH. Post-metalation of PAF-26-COOH yields a series of PAF-26-COOM derivatives(M=Li, Na, K, Mg). Microporous PAF-26materials with high surface area, high porosity andtunable pore size are achieved via a post-metalation method. High adsorption capacities towardCO2and CH4are demonstrated with as-prepared PAF-26materials, while very low uptake for N2is measured with the same samples. Additionally, an enhanced adsorption for CO2and CH4isobserved for PAF-26-COOM in comparison with PAF-26-COOH, which indicates thatintroduction of light metal ions would improve the adsorption affinity to CO2and CH4gases.Further, PAF-26materials exhibit very high isosteric heats of adsorption toward CO2and CH4.Interestingly, the isosteric heats of adsorption for CO2follow a sequence of PAF-26-COOMg <PAF-26-COOLi<PAF-26-COOK <PAF-26-COONa, which matches well with theircorresponding basicities. The stronger interaction between CH4molecules and PAF-26-COOM is verified by their higher isosteric heats of adsorption, which is due to the higher polarity of metalions than that of protons and the small-pore effect. The selective adsorption toward CO2and CH4over N2is studied and the predicted selectivity is calculated by the IAST model derived from theiradsorption isotherms. All measured PAF-26samples show high selectivity for CO2over N2andsignificantly high selectivity for CH4over N2. The combined merits of high sorption capacity andhigh selectivity make PAF-26as a potential stepping stone for carbon capture and storage.2. Small hydrocarbons (C1, C2and C3) are important energy sources and chemical feedstock inpetrochemical industry. Before transportation and utilization of these resources, they must undergoprocessing for upgrading and purification from their raw gases mixtures. In this part, wesuccessfully synthesize novel ZnP-PAF materials through ionothermal reaction. By controllingsynthesis temperature, the tunable surface areas and pore sizes of ZnP-PAF materials are achieved.More valuably, ZnP-PAF materials show different adsorption capacities for the smallhydrocarbons according to the number of carbon atoms. The selective hydrocarbons adsorption ofZnP-PAF materials are demonstrated by IAST prediction. Furthermore, we explore the utility ofZnP-PAF-400for high performance GC separation of small hydrocarbons mixture owing to theirdifferent van der Waals interactions and polarizability. The fast dynamic breakthrough tests furtherprove the ZnP-PAF-400and ZnP-PAF-500can separate the small hydrocarbons based on theirhierarchical isosteric heats in an actual adsorption-based separation process. For the first time, wesystematically investigated POFs for the hydrocarbons separation under both equilibrium andkinetic conditions. The high separation capability and selectivity offers ZnP-PAF-500as apromising candidate for energy efficient separation of small hydrocarbons in PSA process.We have also successfully synthesized a new microporous crystalline material (MCOF-1) with anarrow pore size of0.64nm. MCOF-1possesses architectural stability and porosity afterevacuating solvent molecules. Additionally, MCOF-1shows high adsorption capacity for the C2H4,C2H6and C3H8. More valuably, MCOF-1exhibits a significantly high selectivity for C3H8overCH4and high selectivities for C2H6and C2H4over CH4, respectively. It is expected that thepreparation of porous material with suitable pore size could be promoted for small hydrocarbonseparation.3. As so far, most of the porous networks are insoluble and research on the implementation ofthese materials mainly hinges on to use them in powder forms. This insolubility of POFs similarlyhinders them to be employed for the fabrication of diverse kinds of devices such as porousfilm/membrane for potential future applications. In this part, we have developed a cost-effectivestrategy to prepare triazine-based porous powder (TPP) and triazine-based fluorescent porousmembranes (TPM-1). The TPP with lager surface area shows a larger adsorption capacity for CO2and high CO2/N2selectivity. The N2adsorption isotherm of TPM-1demonstrates that membranepossesses intrinsic micropore and narrow pore size (6.6). CO2and N2sorption measurementsand IAST calculations show that both TPP and TPM-1have high sorption affinity toward CO2 owing to its narrow pore size and N-containing active sites in triazine groups. The as-preparedTPM-1membrane is further applied for CO2separation. Gas separation results reveal that thetriazine membrane exhibits high separation factor with high CO2permeability. Moreover, TPM-1membrane preserves its separation performance after a long-time test. Our work offers aconvenient and low-cost way to prepare N-containing porous membrane, showing its potential inpractical CO2capture application.