Design And Preparation Of Covalent Triazine Frameworks For Gas Adsorption And Separation

Porous materials have high specific surface area and large pore volume,and have been widely studied in terms of gas adsorption separation,hydrogen storage,and the like.Especially,the covalent triazine frameworks?CTFs?have received extensive attention due to their unique heteroatom aromatic ring structure,good pore size adjustability and high thermal and chemical stability.In this dissertation,the typical mixed gas separation requirements including carbon capture,natural gas purification,and ethylene feed gas purification are targeted to regulate the functional groups,pore size,and skeleton composition of CTFs.We found that under certain conditions,the smaller the pore size,the better the adsorption and capture of the gas,and the material containing the hierarchical porous structure is more beneficial to obtain high separation performance when the gas is adsorbed and separated.To sum up several factors,this dissertation designs and synthesizes several different structures of covalent triazine frameworks,and tests the selective adsorption performance of each material for different gases,specifically divided into two aspects:?1?A novel porous organic polymer?CTF-PO71?was synthesized by ionic thermal polymerization using a commercially available high performance pigment?Pigment Orange71,PO71?as a monomer.CTF-PO71 has abundant functional groups,including C-H,C?N,C=O and N-H,possesses high thermal stability and oxidation resistance,and has hierarchical porous structure combining with micropores and mesopores.CTF-PO71 can preferentially adsorb acetylene?C₂H₂?over ethylene,and kinetic breakthrough experiments show that CTF-PO71 can selectively enrich C₂H₂ in C₂H₄/C₂H₂?99:1?mixture to achieve high purity ethylene feed gas in low-cost.The functional sites with different electrostatic potentials on the pore surface of CTF-PO71 demonstrate a strong interaction between C₂H₂ and CTF-PO71 to achieve preferential adsorption of C₂H₂ over C₂H₄,thus enabling effective capture of a trace amount of C₂H₂ from the gas mixture.?2?New carbon-based materials with narrow ultramicropore?size<7??distributions?>95%?and high N doping contents are fabricated through the pyrolysis of a perchloro-substituted porous covalent triazine-based framework?ClCTF-1-400?.In particular,the sample prepared at 650^oC?ClCTF-1-650?possesses the highest ultramicropores content?98%?and large N content and demonstrates a very high CH₄ and CO₂ capacity,as well as a low N₂ uptake under ambient conditions.The extraordinarily high CH₄/N₂ and CO₂/N₂selectivities correlate with both the ideal adsorption solution theory?IAST?method and performed dynamic separation experiments?breakthrough experiments?.The results reported in this study far exceed the CH₄/N₂ and CO₂/N₂ selectivities of previously reported carbon-based adsorbents including various of nitrogen-doped polymers.These results are believed to be associated with the unusually high N content,as well as the suitably narrow ultramicropore size distribution.