Design and synthesis of conjugated microporous polymers for environmental applications

Abstract

Porous polymers have been attracted a great deal of attention because of their importance in established processes such as catalysis and molecular separations and in emerging technologies for energy and environment. Especially, the tremendously growing demand for energy throughout the world make great developments of conjugated microporous polymers (CMPs) due to their unique properties of permanent microporous structures (below 2 nm) and π-electronic delocalized backbone for the simultaneous transport of charges and materials. Up to date, a wide variety of methods to synthesis for CMPs has been introduced by means of non-metal- and metal-catalyzed polymerization. However, the need for metal catalyst to construct robust C-C linkages hinders scalability of materials due to the high-cost, and residual metals can impinge on the porous structure. Moreover, controlling electronic properties of CMPs by varying monomers has been remained a challenge to attain optimum band gap suited for target application ？ water splitting ($E_g$ = ~1.9 eV), $CO_2$ reduction ($E_g$ = ~2.2 eV), and photovoltaic solar systems ($E_g$ = 1.65 - 3.27 eV for full visible-light absorption) - because of the lack of quantitative relation between the band gap and monomer structures. In my thesis, I proposed a powerful strategy to precisely tailor the band gap of CMPs in a systematic manner via metal free C-C polymerization. In chapter 1, I summarized the development of porous polymers and some of the advantages and disadvantages of different types of porous polymers. I also highlighted a diverse range of synthetic routes, and structural merits of porous polymers to utilize in various fields. In chapter 2, I introduced novel synthetic strategy to tune optical band gap of CMPs, namely acidity dependent In-situ cyclization, which is combined with a Schiff base polymerization and subsequent dehydrogenation reaction of cyclization controlled by the acidity of acid catalyst. In chapter 3, the resulting CMPs were evaluated in terms of structure, electronic properties, and textural properties. I believe that the design and synthesis of conjugated microporous polymers (CMPs) will show great potential for the future in the field of environmental applications.