Synthesis Of Covalent Triazine Frameworks And Their Applications In Adsorption And Separation Of Carbon Dioxide And Detection Of Metal Ions

As a subtype of porous organic polymers（POPs）,covalent triazine frameworks（CTFs）structurally composed of triazine units have attracted attention due to the highly porosity and excellent stability.CTFs have a wide range of application prospects in adsorption and separation of carbon dioxide,detection of metal ions,catalysis of organic reactions and so on.CO₂emissions are regarded as the main contributor to the climate change.The development of effective methods and materials for CO₂capture and storage（CCS）from industrial sources is a crucial task.The functionalization strategies of CTFs include bottom-up synthesis and post-synthetic.However,the studies on post-synthetic functionalization of CTFs for CCS are scarce yet.Many biological processes require the participation of Fe³⁺,which is one of the important metal ions in biological and environmental systems.The fluorescent sensors for the detection of metal ions have attracted considerable interest due to easy operability as well as high sensitivity and selectivity.Therefore,it is of great significance to explore luminescent materials as chemical sensors.However,there are only a few reports on POPs as fluorescent sensors to detect Fe³⁺.This thesis is devoted to the research on the functional synthesis,properties and applications of CTFs.The main research contents of each chapter are as follows:1.The hydroxyl-appended CTF（BCM-CTF）was synthesized by ionothermal method using the cyano monomer bis（4-cyanophenyl）methanol（BCM）,and then the ethylenediamine（EDA）modified CTF（BCM-CTF-EDA）was synthesized through borrowing hydrogen strategy by post-synthetic.When hydroxyl groups were substituted by EDA groups,the CO₂adsorption capacity（68 vs 164 mg/g,at 273 K and 1 bar）and CO₂/N₂selectivity（35 vs 73,273 K）were significantly increased.Fourier transform infrared（FTIR）spectrum of BCM-CTF-EDA after CO₂adsorption indicated that the adsorption process was chemisorption,resulting in high energy consumption in the material regeneration process.2.The carbonyl-appended CTF（BCK-CTF）was synthesized by ionothermal method using bis（4-cyano）ketone（BCK）containing carbonyl group.Glycine（Gly）was grafted into the pore by post-synthetic to obtain an amino acid functionalized CTF（BCK-CTF-Gly）.The molecular structures of two CTFs were determined by means of fourier transform infrared（FTIR）,X-ray photoelectron spectroscopy（XPS）and so on.BCK-CTF-Gly showed significantly improved CO₂adsorption capacity compared with BCK-CTF（245 vs 145 mg/g,at 273 K and 1 bar）.The Q_stvalue of BCK-CTF-Gly was 33.3 k J/mol,which was proved to be physisorption in combination with the in-situ infrared spectrum.Therefore,BCK-CTF-Gly can be completely regenerated after 30 minutes of vacuum treatment at 333 K,and it still exhibits stable CO₂adsorption performance after ten adsorption-desorption cycles.3.A covalent triazine framework FL-CTF composed of electron-donating thiophene units and electron-accepting benzothiadiazole units was synthesized by Suzuki coupling reaction.The chemical structure of FL-CTF were revealed by a combination of FTIR,solid-state ¹³C NMR,and XPS.The as-prepared FL-CTF shows fluorescent properties and can selectively recognize Fe³⁺with the detection limit of0.78μM.The selectivity,sensitivity,regeneration and fluorescence quenching mechanism of Fe³⁺were studied by a series of fluorescence,UV-Vis absorption spectra and XPS measurements.