Synthesis And Properties Of N-Containing Conjugated Microporous Polymers

As a typical representative of porous organic polymers,conjugated microporous polymers(CMPs)not only perfectly combine porosity with extended conjugated networks,but also possess high stability and various synthetic strategies,which have been widely used in many fields.Function-oriented,CMPs with specific target properties can be successfully synthesized by transforming the building units.Besides,a variety of functional groups can be introduced into the established CMPs framework through post-synthetic modification(PSM)strategy.The introduction of nitrogen atoms can enrich the structure of CMPs,and then endow them excellent properties and applications.By analyzing the relationship between structure and performance,a series of CMPs materials were designed and synthesized using different nitrogen-containing building blocks through direct polymerization or PSM strategies.And the applications of these CMPs in light-responsive oxidase mimic,iodine capture,dyes and gas adsorption/separation were systematically explored.The main results were summarized as follows:1.A pyrazinoquinoxaline-based CMP was designed and synthesized through Suzuki coupling,and exhibited excellent oxidase mimic catalytic activity under visible light irradiation.It is the first work to use CMP as light-responsive oxidase mimic for biological enzyme fluorescence sensors.Under the visible-light irradiation,CMP employed dissolved oxygen as electron acceptor to generate superoxide radicals for easily oxidizing thiamine to generate dehydrothiamine with blue fluorescence,and this catalytic process was highly pH dependent in the range of 4.6-8.6.Urease can hydrolyze its corresponding substrate to trigger a change of pH.Hence,a sensing platform of urease was constructed.The detection limit of this method is 0.42 U L^-1,and this method was also used for the analysis of urease in actual saliva samples.Based on the above work,a pyrazinoquinoxaline-containing D-?-A CMP was synthesized as a light-driven oxidase mimic for the colorimetric sensing of glutathione(GSH).CMP can effectively oxidize the colorless TMB to blue ox-TMB under visible light,while glutathione can effectively inhibit the progress of the catalytic reaction.Therefore,the CMP/TMB system can realize the colorimetric sensing of reduced glutathione.The quantitative detection range of GSH is 0.2-20?M,and the detection limit is 0.06?M.This method was also used in the application of GSH analysis in human serum samples,which exhibited its prospect in actual detection.These two works not only enriched the structural types of light-responsive CMPs,but also opened the prelude to the use of CMPs materials as light-responsive mimic enzymes in the field of biomedical sensing.2.In order to prepare adsorbents with high-efficiency iodine adsorption capacity,we synthesized three CMPs based on triphenylamine derivatives through Pd-catalyzed Sonogashira and Suzuki coupling reactions.The resulting polymers possessed high BET surface areas(up to 1185 m² g^-1).Due to their excellent pore properties,electron-rich?-conjugated network structure,and the interaction of N atoms and I₂ molecules in the framework,CMPs exhibited high iodine vapor capture performance and good recyclability after ethanol washing.Then,two CMPs containing pyridine were synthesized using the Suzuki coupling reaction.The highest BET surface area was 2028 m² g^-1,and the capture capacity of iodine vapor was 5.29 g g^-1,which is more prominent compared with the previously reported literatures.These CMPs also exhibited good recyclability.The high adsorption capacity can be attributed to the combined effect of the excellent porosity,the effective adsorption sites,and the extended?-conjugated network framework.In addition,these materials combined the sensing and adsorption functions of tetracycline,which can be used as new fluorescent probe for detection of tetracycline,and at the same time,it also showed high tetracycline adsorption capacity.3.We provided a post-synthetic modification(PSM)strategy to construct cationic conjugated microporous polymers.First,the phenyl conjugated microporous polymer(CMP-O)was synthesized by using 1,3,5-tribromobenzene and terephthalic acid.In the first PSM step,chloromethyl was introduced through Blanc chloromethylation,and in the second step,N-methylimidazole reacted with chloromethyl to construct an imidazolium-containing cationic skeleton(CMP-Im).The porous,conjugated and cationic skeleton of CMP-Im facilitated its interaction with anionic dyes.Hence,CMP-Im exhibited effective adsorption of such as methyl orange(MO)and congo red(CR),and the adsorption capacities were 588 and 2500 mg g^-1 for MO and CR,respectively.Besides,it possessed the ability to selectively adsorb the mixed liquid of MO and methylene blue(MB),and the mixed liquid of CR and MB.In addition,we use CMP-O as the precursor,dichloromethane and chloroform as cross-linking agents.The intermediates were obtained by AlCl₃-catalyzed Friedel-Crafts alkylation reaction,which not only increased the BET surface areas,but also introduced the functional group of chloromethyl.Then the next step was to introduce CO₂-philic diethylenetriamine.Taking the first modification of chloroform as an example,the BET surface area increased from the initial 1182 m² g^-1 to 1828 m² g^-1,and the CO₂ adsorption capacity improved from 2.58 to 4.92 mmol g^-1(1 bar,273 K).Besides,after modifying the polyamine group on the pore wall,the adsorption of CO₂increased from 19.50 to 37.07 k J mol^-1,and the selectivity of CO₂/N₂ increased from16.68 to 48.70(1 bar,273 K,).These two works constructed N-containing CMPs through easily available post-synthetic modification strategies,which improved their performance in dyes and gas adsorption,and provided meaningful guidance for the functionalization of CMPs.