Preparation of Microporous Polymers by Metal-Catalyzed Coupling and Thiol-Yne Addition Reactions of Multifunctional Building Blocks

Abstract

Microporous organic polymers with high surface areas and physicochemical stability have potential applications in gas storage, catalysis, and separation. In this study, various microporous polymers were prepared by thiol-yne addition reaction and metal-catalyzed carbon-carbon bond forming reactions of multifunctional organic compounds. A microporous polymer was synthesized by thiol-yne addition reaction of tetrakis(4-ethynylphenyl)adamantane and benzene-1,3,5-trithiol in the presence of AIBN. Au nanoparticles (Au NPs) were prepared by NaBH4 reduction reaction of HAuCl4 and immobilized in the polymer network via an interaction with sulfur groups. The BET surface area of the microporous polymer was 576 m2/g and decreased to 104 m2/g after incorporation of the Au NPs. The Au NPs loaded microporous polymer showed a catalytic activity in hydrogenation reaction of 4-nitrophenol. A bisphenol-A imprinted microporous polymer was prepared by Yamamoto cross-coupling reaction of tetrakis(4-bromophenyl)methane and a bromophenyl-bisphenol-A (template) complex. After the extraction of the template molecules, the BET surface area of the polymer increased from 25.3 m2/g to 562 m2/g. The specific recognition ability of the polymer to bisphenol-A and its structural analogues was investigated by HPLC analysis. The imprinted polymer showed a high rebinding ability of bisphenol-A compared with that of non-imprinted polymer. In kinetic study, a 90 % of an equilibrium amount was recognized within 5 min after the addition of bisphenol-A. Microporous polymers, TPE-DB, TPE-TB, and TPE-AD were prepared by Sonogashira-Hagihara cross-coupling reaction of tetrakis(4-iodophenyl)ethane (TIPE) with 1,4-diethynylbenzene (DB), 1,3,5-triethynylbenzene (TB), and tetrakis(4-ethynylphenyl)adamantane (AD), respectively. Polymers, TPE-DB/TB(1:2) and TPE-DB/TB(3:2), having two different ethynyl units were also obtained by using mixtures of 1,4-diethynylbenzene and 1,3,5-triethynylbenzene in molar ratios of 1 : 2 and 3 : 2, respectively, for the coupling reaction. Among the polymers with the one type of ethynyl units, TPE-TB showed the highest BET surface area of 1230 m2/g, followed by TPE-DB (405 m2/g) and TPE-AD (615 m2/g). TPE-DB/TB(3:2) with two different ethynyl units exhibited a significantly enhanced BET surface area of 1840 m2/g compared with TPE-DB and TPE-TB. The polymers except TPE-DB showed CO2 and H2 uptakes over 40 and 100 cm3/g, respectively. Microporous polymers were obtained by Heck cross-coupling reaction of 1,3,5-trichlorobenzene or 1,3,5-tri(4-bromophenyl)benzene with divinylbenzene. The PCP pincer complex was synthesized from Pd(COD)Cl2 and C6H4-2,6-(OPiPr2)2 and used as a catalyst for the reaction. After carbonization, the volume fraction of micropores with a diameter less than 1 nm increased and the polymers showed the enhanced CO2 and H2 uptakes.