Microporous Organic Polymers For Carbon Dioxide Capture

Global warming caused by large CO2emission has an alarming impact on the earth’s fragile environment. In order to stabilize the CO2concentrations in the atmosphere, carbon dioxide capture has attracted the interests of international in recent years, and the development of efficient methods for capturing CO2from industial flue gas has become an important issue. Microporous materials have potential applications for CO2capture due to many advantages such as low density, high specific surface areas and high porosity. Siginificant progress has been made in recent years on these materials, especially on the design and synthesis of microporous organic polymers (MOPs). To date, however, most monomers used in construction of the MOPs should be carefully designed and synthesized. Moreover, toxic solvents or/and catalysts are usually used during the reaction process. All these factors are prone to limit the wide use of the MOPs in industry. Therefore, the synthesis of cost-effective microporous polymers with high surface area is still a major challenge for chemists and materials scientists.The main task of this PhD thesis is to synthesized several hypercrosslinked polymers under mild reaction conditions by using cheap commercially chemicals as starting monomers. The polymers are characterized by solid-state13C NMR, N2gas sorption, and FT-IR spectroscopy. In addition, the CO2-capture applications of these porous organic compounds have also been studied. The main contents are listed as follows:(1) Two hypercrosslinked polymer networks has been synthesized by the self-condensation of bishydroxymethyl monomer,1,4-benzenedimethanol (BDM), and monohydroxymethyl compound, benzyl alcohol (BA). This is different from the previous reports that multifunctional monomers or crosslinkers is crucial for constructing the porous polymer networks. N2sorption isotherms for the polymers showed that both materials are predominantly microporous with the Brunauer-Emmett-Teller (BET) surface areas of847m2g-1for HCP-BDM and742m2g-1for HCP-BA. At273K/1bar, the CO2uptake was about12.6and8.46wt%for HCP-BDM and HCP-BA, respectively. Based on these results, this study opens up the possibility of synthesizing porous materials using the monofunctional monomers.(2) A series of porous polyimides with surface area up to660m2g-1have been synthesized by polycondensation of melamine and several readily available dianhydride monomers. Notably, the polymerization was carried out without toxic catalysts. Moreover, all of the starting compounds used in this study are low price, whereas other porous polyimides prepared often require expensive twisted (spiro type) or tetrahedral-based monomers. The environmental application of the polymers have also been investigated and it was found that PI1can adsorb7.3wt%CO2at273K/1.13bar.(3) The incorporation of heteroatoms into the porous polymers has the potential to increase the sorption and the selectivity for CO2. With this consideration in mind, we reported a facile and versatile strategy for preparing aromatic heterocycle-based microporous organic polymers. Unlike the elaborately designed monomers used in previous studies, all the heterocyclic molecules were directly crosslinked to form the highly porous networks by using formaldehyde dimethyl acetal (FDA) as external cross-linker. Considering their moderate surface areas, all these materials demonstrate ultrahigh CO2storage properties compared to other microporous with comparable surface area in the range of400～700m2g-1. Specifically, the network based on pyrrol (Py-1) shows an extraordinarily high selective adsorption of CO2over N2(about178at273K). To our knowledge, this value is the highest among all microporous materials reported to date.(4) The synthesis of a microporous organic polymer containing free-base porphyrin subunits has been accomplished by coupling the meso-tetraphenylporphyrin with Lewis acid as the catalyst. Metallation by post-synthesis modification affords microporous materials incorporating either Mg or Zn(porphyrins) that have been shown to be benifited to the CO2uptake.