Design And Prepartation Of Functionalized Metal-organic Frameworks Composite For Toxic Gas And Water Adsorption

Metal-organic frameworks（MOFs）are porous nanocrystalline materials self-assembled by organic ligands and inorganic metal ions through coordination bonds.MOFs have developed rapidly due to easy functional modification,highly tunable pore size,high specific surface area,and outstanding hydrothermal stability,attracting the research interest of scholars,making them very attractive.It has been widely used in many fields.The adsorption and separation gas are of great significance to industrial progress and human health.And solid adsorbents play a great role in the process of gas adsorption and separation.This paper addresses the adsorption of three polar gases,such as ammonia（NH₃）,sulfur dioxide（SO₂）,and water vapor（H₂O）,excellent MOF composites were obtained by using different methods,and the adsorption and separation performance of different gases was explored.The main work include:1.Different ionic liquids（ILs）with multiple adsorption sites for the polar gas（NH₃）were designed,and then the porous support was selected as the MOF material:MIL-101（Cr）.By loading different ILs and increasing the loading of ILs on MOF,more NH₃ adsorption sites were presented.The experimental results show that the adsorption capacity of the obtained IL@MIL-101（Cr）composite is improved with the increase of the ILs content,and the NH₃ adsorption capacity finally can up to 26.58 mmol/g.Therefore,the introduction of ILs-modified MOF materials is beneficial to the NH₃adsorption and storage,at the same time,it improves the NH₃adsorption capacity of MOF materials under low pressure and removes low-concentration NH₃.2.Alkaline IL（[BOHmim]Cl）with multiple action sites for acidic and polar gas SO₂ was designed,and then MOF material was selected as porous carriers to support ILs.The designed IL@MIL-101（Cr）composites can be used for selective adsorption of SO₂ The results show that the obtained IL@MIL-101（Cr）-70%composite has an SO₂ adsorption capacity of 13.18mmol/g.The adsorption capacity at 0.01 bar is 3.3 times higher than MIL-101（Cr）.It hardly adsorbs CO₂（0.26 mmol/g）and N₂（0.07mmol/g）at1 bar,therefore,it can achieve molecular sieving of SO₂,CO₂ and N₂.3.ILs with different adsorption sites for high polarity gas H₂O were designed and introduced into MIL-101（Cr）for functionalization.By introducing multiple adsorption sites,MOFs can show a large number of exposed adsorption sites on their surface and pores to improve the adsorption performance of H₂O,and by utilizing the different solubility of ILs for H2O,the ILs inside the MOFs can provide osmotic pressure to drive water to migrate from the surface to the interior during the water absorption process to achieve a dynamic equilibrium,thereby achieving a confinement-unconfinement transformation of ILs.Therefore,loading ILs on MOFs can overcome the limitation of pore volume and overcome its the mass transfer problem,thereby obtaining better water vapor adsorption performance.The results display that the IL@MOF composites obtained using[BOHmim][Zn₂Cl₅]with multiple adsorption sites and good hydrophilicity can achieve high water absorption capacity（477 wt.%,RH=95%）at 298 K and Therefore,the combination of finely designed MOFs with hygroscopic liquid media ILs can be a potential alternative for trapping highly polar molecules.