Synthesis And Carbon Dioxide Adsorption Performance Of MOF-74 Derived Carbon Materials

In this study,we firstly prepared porous carbon materials with constant crystal morphology by high-temperature charring using the pore structure of MOF-74 crystals themselves,and obtained a series of carbon materials with multi-level pores derived from MOF-74 crystals（MOF-74-T）by controlling the charring temperature（300°C-600°C）.The sample carbonized at 900℃for 1h（MOF-74-900）had an excellent CO₂ adsorption capacity（3.64 mmol/g,1bar,273 K）compared to samples obtained at other temperatures.The SEM and EDS results of the MOF-74-900 porous carbon material show that the synthesised crystals have a typical hexagonal rod structure and maintain their skeletal structure without collapse and disintegration even after high temperature charring,and that the carbon content of the MOF-74-T porous carbon material increases with temperature.The results of X-ray diffraction（XRD）patterns show that the synthesised crystals were compared with standard cards,demonstrating the successful synthesis of MOF-74 crystals,and that with the increase in charring temperature,MOF-74-T lost the diffraction peaks of the original MOF-74crystals,generating Zn O nanoparticles.The results of Raman testing of the MOF-74-T porous carbon materials show that by carbonization at high temperatures,MOF-74 crystals are successfully converted into carbon materials.The results of the TG and FI-TR tests on the MOF-74-900 porous carbon material show that the main loss of material mass during the charring process comes from the dissociation of ligands,and the loss of solvent molecules.The results of the BET test on MOF-74-900 porous carbon material also explain the high CO₂ adsorption capacity of MOF-74-900 porous carbon material.As the MOF-74-900 porous carbon material was found to have excellent adsorption of carbon dioxide molecules in the previous content,this chapter investigates the preparation of PEKC-20%MOF-74 carbon aerogel by co-carbonisation of MOF-74 crystals with phenolphthalein-based polyaryl ether ketone（PEKC）to further improve the adsorption performance of the porous carbon material on carbon dioxide gas.A series of tests have shown that the prepared PEKC-20%MOF-74 carbon aerogel has high thermal stability and has been shown to be suitable for CO₂ adsorption due to its ultra-high BET specific surface area（2317.25 m²/g）,as well as a microporous volume of 0.22 cm³/g and an average pore size of 0.55 nm,with microporosity of less than 0.8nm.The excellent physical properties of the PEKC-20%MOF-74 material mentioned above,resulted in a carbon dioxide adsorption capacity of 3.79 mmol/g and 5.1 mmol/g for PEKC-20%MOF-74 carbon aerogel at 1 bar,298 K and 273 K respectively.This indicates that the new porous carbon produced by carbonising the MOF crystals and co-carbonising them with a polymer can be used to adsorb carbon dioxide gas.The new porous carbon can have a great improvement in the adsorption capacity of CO₂ gas,and the stability of the carbon material makes it promising for practical applications as well.