Design And Preparation Of Functional Mesoporous Carbons And Porous Ionic Liquids And Their Applications In Gas Adsorption

With continuous development of the human society,porous materials are playing an increasingly important role in all areas of human production and life.However,traditional porous materials(silica gel,activated carbons,etc.)have gradually exhibited their disadvantages such as poor pore orderness,difficulty in surface functionalization,limited types,leading to serious contradiction between developing application requirements and traditional porous materials,and rational design and high-efficient preparation of new porous materials has become one of the most popular research topics among the world.Therefore,this article mainly focuses on the rational design and high-efficient preparation of new porous materials.,and the main content can be divided into the following two aspects:Mesoporous carbon materials feature high specific surface area,large pore volume and high chemical stability.Owing to these outstanding properties,they have broad application prospects in various fields such as catalysis,separation and energy storage.However,current method for preparing the mesoporous carbon material has some obvious disadvantages such as complicated preparation process,solvent consumption,raw material toxicity,which greatly limits its further development and application.Therefore,a new mechanochemical coordination method is adopted to use environmentally-friendly biomass tannins as carbon sources,different alkaline earth metal salts as coordination cross-linkers,and F127 as a soft template to synthesize a series of alkaline earth metal oxide-functionalized mesoporous carbon materials under solvent-free conditions.The ordered mesoporous carbon materials were characterized by infrared,small-angle X-ray scattering,N2 adsorption,electron microscopy and other characterization methods to explore the synthesis mechanism and structural characteristics of the synthesized carbon materials,and meanwhile some key factors such as the existence and type of soft template agents,the type and amount of metal salt,the existance of alkaline earth metal oxide on the synthesis of ordered mesoporous carbon and pore structure were systematically investigated.Moreover,the adsorption and separation performance of the synthesized carbon materials were also evaluated.The results show that the prepared mesoporous carbon material has a specific surface area between 273 and 707 m2/g with main mesopore size ranging from 7 to 10 nm,and basic CaO and MgO nanoparticles(particle size:2 to 5 nm)were highly dispersed in the skeleton and pores of carbon materials.The presence of metal salts and soft template plays a key role in the formation of ordered mesopore structures,and structural properties such as specific surface area and pore size of the materials can be effectively adjusted by changing the type and amount of metal salt and templating agent In addition,the synthesized ordered mesoporous materials exhibited high-efficient adsorption peformance of methyl blue(MB)and methyl orange(MO)dye molecules in aqueous solution(541 mg/g and 435 mg/g).The adsorption capacity for CO2 gas is up to 3.08 mmol/g(273K,1 bar),and the IAST separation selectivity for CO2/N2 mixture is up to 72(v/v,5:95).Moreover,this mechanochemical coordination self-assembly method was further adopted to use tannins as the main carbon source,metal salts as coordination cross-linker,and the organic small molecules containing different coordination functional groups as nitrogen sources in the preparation of nitrogen-doped mesoporous carbon materials.The structural characteristics of the synthesized nitrogen-doped mesoporous carbon materials were studied in detail by different characterization mehods such as thermogravimetry,small-angle X-ray scattering,N2 adsorption,electron microscopy and XPS.The key parameters such as the species and dosage of nitrogen source on he microstructure and composition of the mesoporous carbon were systematically investigated.The adsorption and separation abilities of CO2 and low-carbon hydrocarbon gases waere evaluated on these mesoporous carbon materials.The results shows that the mesopore size of mesoporous carbons tend to increase as the amount of nitrogen source increases.In addition,the mesoporous carbon structure is also greatly influenced by the type and density of coordination groups of nitrogen-source molecules.In general,a stronger coordination ability of the source molecule could lead to a more concentrated mesopore size distribution.The static adsorption experiments of CO2 and light hydrocarbon gases show that the introduction of nitrogen-containing functional groups can effectively increase the interaction between mesoporous carbon and acidic CO2 molecule,leading to a high adsorption capacity(up to 3.45 mmol/g at 273 K),and the LAST separation selectivity of CO2/N2(15:85,v/v)is about 30.Moreover,these nitrogen-doped mesoporous carbon exhibits excellent adsorption capacity for low-carbon hydrocarbon gases,and preferentially adsorb alkyne gases.On the other hand,traditional porous materials generally exist in solid state,making it difficult to couple them into common industrial liquid circulation systems.Recently,researchers have successfully developed porous liquid materials,which thus provides new ideas for solving the above problems.However,porous liquid materials reported so far still have some obvious disadvantages such as limited types,complicated preparation process,and easy decomposition of porous units,which greatly hinders their further development.However,the porous liquid materials reported so far still have the disadvantages of small number of species,complicated preparation process,and easy decomposition of porous units,which hinders their further development.In this paper,a series of novel porous liquid materials containing metal organic frameworks and molecular sieves were designed and prepared.The design strategy was proposed and its application performance in gas storage and separation was explored.The results show that the[DBU-PEG][NTf2]ionic liquid with large-sized bicyclic cation structure is used as a solvent medium to provide fluidity,and porous framework material nanoparticles such as ZIF-8 and ZSM-5 are used as porous host units.In a liquid environment,the ordered microporous network of porous units can effectively block liquid ions larger than the pore size from entering the pores to form permanent pores that are not filled,and at the same time there are non-covalent interactions(coordination force,van der waals force,etc.)between nanoparticle-ionic liquids can inhibit the aggregation and sedimentation of the nanoparticles,and finally a stable porous liquid system could be prepared by simple and effective solution mixing.The results of positron lifetime lifetime spectroscopy test demonstrated the presence of permanent pores in porous ionic liquids.The results of high pressure gas adsorption experiments showed that the gas adsorption capacity of porous ionic liquids can be effectively controlled by adjusting the type and mass ratio of porous framework materials,and the gas desorption process exhibits obvious hysteresis loop;in addition,the gas separation selectivity of the ZIF-8 type porous ionic liquid to the CO2/N2 system is as high as 60(adsorption capacity ratio),which is almost 8 times that of pure ZIF-8 porous framework materials.This new class of liquid porous materials opening up new opportunities in the development of new separation technology platforms.