Fabrication And Application Of Porous Organic Frameworks And Their Derived Porous Carbons

Bearing excellent physical and chemical stabilities,high specific surface areas,and designable controllable synthesis,porous organic frameworks rapidly became the hot topic in scientific research.From design and preparation of the new-structural porous organic frameworks to preparation of porous organic frameworks with different functionalization,researchers never stop for a moment.Porous organic frameworks have been widely used in energy storage and conversion.Preparation of porous carbon materials by carbonized porous organic frameworks not only can mantain the characterization of porosity but also hold the advantage of high electric conductivity which is very common in carbon materials.Porous carbons prepared from porous organic frameworks by carbonization exhibit excellent performances in the field of the environmental protection,such as,gas adsorption and storage;Based on the advantages of high conductivity and abundant porousity,porous carbons have been widely applied to the field of energy storage,such as lithium batteries.From the point of view of preparation of new structural porous organic frameworks,we successfully prepare a neutral organic framework and three charged porous organic frameworks and investigate their gas adsorption performances at low pressure.At the meanwhile,high carbon content porous organic frameworks with high thermostability and precise stoichiometric ratio of elements have been used to prepare porous carbons by one-step carbonization method.In order to explore their advantages,the gas adsorption capacities and electrochemical energy storage capacity were studied.The main contents of this thesis are as follows:In the second chapter,selecting the 3,3',5,5'-tetrabromo-1,1'-biphenyl as the building block,and using Yamamoto Ullman coupling reaction,we successfully prepare a new neutral organic porous framework,namely PTBBP.FT-IR spectrum,PXRD,and ¹³C CP MAS NMR analysis have been used to prove that the target material is successfully prepared by effective polymerization.The gas adsorption performances of CO₂,CH₄ and H₂ has identified that the PTBBP can be used as solid adsorbent at low pressure.In the third chapter,we synthesize a series of charged porous organic frameworks,namely B-POF,BP-POF and P-POF,via Yamamoto-type Ullmann cross-coupling reaction from tetrakis?4-bromopyrazolyl?potassium borate and tetrakis?4-chlorophenyl?phosphium bromide as building blocks in different mole ratios.The charge and heteroatoms in the porous frameworks help to increase their isosteric heats of gas adsorptions,and therefore exhibit a good performance of gas adsorption.In the fourth chapter,eight porous carbons have been successfully prepared by directly carbonization of four porous organic frameworks under nitrogen atmosphere at 800 and 1000 ^oC.Comparation of the gas adsorption performances of eight porous carbons under low pressure,we found that the CO2 and H2 adsorption capacities slightly increased and CH₄ adsorption capacity was significantly improved.The enhancement of CO₂ adsorption capacity may be due to the increased afiinity between the host frameworks and CO₂ molecules after carbonization.The reason for the significantly increase of CH₄ adsorption performance can be attributed to the improvement of the isosteric heats of CH₄.The higher isosteric heats of CH₄ is much favor to the adsorption of CH₄.In the fifth chapter,we in-situ prepare three kinds of B-N co-doped,B-N-P co-doped,P doped porous carbons by carbonized B-POF,BP-POF,P-POF.The results show that preparing porous carbons by carbinization of charged porous organic frameworks containing heteroatoms in the inert atmosphere is a relatively simple and high yield route.Besides,we also investigate their performance as electrode materials for supercapacitors applications.All of them showe good performances which is much better than graphene nanosheets.In conclusion,this thesis has been successfully prepared four new structural porous organic frameworks?PTBBP,B-POF,BP-POF,P-POF?via efficient Yamamoto Ullmann coupling reaction by choosing appropriate monomers as building blocks,and all of them show good gas adsorption performances at low pressure.The experimental results show that PTBBP,B-POF,BP-POF,P-POF are potential to be used as gas adsorbents under low pressure.Because of the existence of heteroatoms and charge in the frameworks,B-POF,BP-POF and P-POF exhibit relatively higher isosteric heats of gas adsorption.Based on rich carbon content and excellent stability of porous organic frameworks,we successfully obtain several porous carbons by using directly carbonization method and investigate their gas adsorptions at low pressure,namely,C-PTBP-800,C-PTBP-1000,C-PTBPB-800,C-PTBPB-1000,C-PTBB-800,C-PTBB-1000,C-PTBBP-800 and C-PTBBP-1000.The results show that gas adsorption capacities have increased after carbonization.Porous carbon materials prepared by carbonization of B-POF,BP-POF and P-POF have been explored as electrode materials for supercapacitors.The results have proved that C-B-POF and C-BP-POF can be used as supercapacitor electrode materials,and their performances are superior to the commercial graphene nanosheets.