Synthesis And Properties Of Nitrogen/Oxygen Heteroatom Functionalized Porous Organic Polymers

Porous organic polymers（POPs）are widely used in gas adsorption and separation,heavy metal removal,multiphase catalysis and other fields due to their high specific surface area(S_BET),accurately tunable pore structure and good chemical stability.In particular,the monomers for preparing POPs are cheap and readily available,and the synthesis methods are diverse,which are widely favored.Therefore,it is still a research hotspot to construct POPs with high S_BET and high heteroatom content by using simple synthesis methods.In this thesis,several kinds of heteroatom functionalized POPs were prepared by usual synthesis method with several cheap monomers as the constructed units,and their applications in carbon dioxide（CO₂）adsorption and cycloaddition,iodine（I₂）adsorption were studied.The specific research contents are as follows:（1）A series of triazine-based polymer precursors（TPOPs）were synthesized by simple nucleophilic substitution reaction between melamine and 3,6-dichloropyridazine,2,6-dichloropyrazine,4,6-dichloro-pyrimidine,in which the nitrogen content of TPOP-1 was as high as 46.7wt.%.Furthermore,a series of porous carbon（NPCMs）were prepared by carbonizing at 500℃,600℃ and 700℃ under the protection of N_2.It was found that the NPCMs had higher S_BET（459-1678 m²/g）,pore volume(V_total,0.28-1.60 cm³/g),and nitrogen content（5.0-9.7 wt.%）.The CO₂adsorption experiments showed that the NPCM carbonized at 600℃ exhibited excellent CO₂ adsorption capacity（286 mg/g）and CO₂/N₂selectivity（IAST:38）at 273 K/1.0 bar.Interestingly,there was a strong correlation between the CO₂ adsorption capacity and micropore volume(V_micro,d<1.0 nm),and the correlation coefficient was 0.997;as well the CO₂/N₂ selectivity was linearly correlated with nitrogen content,and the correlation coefficient was 0.976,revealing that V_micro and nitrogen content can improve the CO₂ adsorption capacity and the CO₂/N₂ selectivity of the material.（2）A series of covalent organic polymers HBTA-BDAs were synthesized by the Schiff-base reaction between p-phenylenediamine（BDA）and 2-hydroxy-1,3,5-benzenetricarbaldehyde（HBTA）,2,4-dihydroxy-1,3,5-benzenetricarbaldehyde（DHBTA）and 2,4,6-trihydroxy-1,3,5-benzene-tricarbaldehyde（THBTA）,respectively.The experimental results showed that HBTA-BDAs had higher S_BET（1245-1803 m²/g）,V_total（0.84-1.30 cm³/g）,V_micro（0.25-0.52 cm³/g）,and abundant nitrogen content（16.4-16.9 wt.%）and oxygen content（6.6-12.4 wt.%）.The adsorption results showed that DHBTA-BDA had the highest CO₂adsorption capacity（254 mg/g,273 K/1.0 bar）mainly due to its the highest V_micro（0.52 cm³/g）.And HBTA-BDA had the highest I₂ vapor adsorption capacity（6.27 g/g）,attributing to its higher V_total（1.07 cm³/g）,as well the fact that its pore size was mainly distributed at about 1.4 nm,and there was no pore smaller than I₂ molecular diameter,which eliminated the V_totalwaste caused by pore blockage.This work provides theoretical support for the preparation of CO₂ and I₂ adsorption materials.（3）DHBTA-BDA was functionalized with ZnBr₂ to synthesize metal-functionalized covalent organic polymer DHBTA-BDA-ZnBr₂.It was found that the CO₂ adsorption capacity（160 mg/g,273 K/1.0 bar）of DHBTA-BDA-ZnBr₂ was reduced due to the coordination of the metal,but it had more excellent CO₂ cycloaddition catalytic ability.With the tetrabutylammonium bromide（TBAB）as co-catalyst,under mild conditions（60℃,0.1 MPa CO₂ and 8 h）,DHBTA-BDA-ZnBr₂ could convert 98%propylene oxide into cyclic carbonate.This work provides some theoretical support for the preparation of catalytic materials for CO₂cycloaddition.