Immobilized Amino Ionic Liquids: Preparation, Adsorption And Catalytic Properties

Ionic liquids（ILs） have shown fascinating prospects in gas adsorption, catalytic conversion, and extraction separation due to their extraordinary properties, such as high chemical and thermal stability, excellent solubility, and unique designability. Functionalized ILs containing special functional groups have task-specific functionality, which play an increasingly prominent role in green chemistry. Mesoporous silica materials have been widely used in many fields including catalysis, adsorption and functional materials owing to the ordered pore structure, large specific surface area and high hydrothermal stability. Supported ILs formed by immobilizing functionalized ILs on mesoporous silica materials are eco-friendly and efficient candidates for adsorption, separation and catalytic conversion.In the present work, two amino ILs functionalized organic-inorganic nanocomposites were successfully synthesized for CO₂ capture and conversion, and anionic dyes removal, respectively. The detailed researches and results are given as follows:（1） Preparation of amino ILs functionalized mesoporous SBA-16 silica andits application in CO₂ capture and conversion Amino ILs functionalized mesoporous SBA-16 silica nanocomposite SBA-16@DHIM-NH₂ was successfully synthesized via grafting method to capture and convert CO₂ effectively. SBA-16@DHIM-NH₂ possesses a typical “cage-like” structure, large surface area, and high stability. And the amino ILs is distributed uniformly in the whole internal pore system via chemical bonding in SBA-16. Meanwhile, SBA-16@DHIM-NH₂ exhibits outstanding CO₂ capture and conversion performance under mild conditions. The experimental maximum CO₂ adsorption capacity is 1.07 mmol·g-1 at 75 °C under atmospheric pressure. It is worth noting that the CO₂ adsorption capacity is 0.92 mmol·g-1 even at 120 °C. Furthermore, SBA-16@DHIM-NH₂ displays high catalytic activity in the conversion of CO₂ to chloropropene carbonate under mild conditions. A yield of 96.0 % with 96.9 % selectivity is obtained under the reaction conditions of 120 °C, 2.0 MPa, and 6 h. That is, SBA-16@DHIM-NH₂ shows good performance in CO₂ capture and conversion simultaneously. Moreover, SBA-16@DHIM-NH₂ shows superior stability and recyclability in CO₂ adsorption and catalytic process.（2） Preparation of amino ILs functionalized magnetic mesoporous silica and its application in dye removal Amino ILs functionalized magnetic mesoporous silica nanocomposite Fe3O4@n Si O₂@m Si O₂@DHIM-NH₂ was successfully synthesized viagrafting method to remove anionic dyes effectively. Fe3O4@n Si O₂@m Si O₂@DHIM-NH₂ possesses a typical “core/shell” structure, large surface area, good magnetization, and high stability. And the amino ILs can interact with Fe3O4@n Si O₂@m Si O₂ throughout the whole internal pore system via chemical bonding. Meanwhile, Fe3O4@n Si O₂@m Si O₂@DHIM-NH₂ presents superior adsorption performance and instantaneous adsorption capacity in the process of dye adsorption. The maximum adsorption capacities are reached at p H 2 due to the protonation of amino groups. The experimental maximum adsorption capacities are 153.06 and 84.40 mg·g-1 for orange II and amaranth at 35 °C, respectively. It is found that the adsorption kinetics isotherms are well fitted by pseudo-second-order model and the adsorption isotherms agree well with the Langmuir model. The electrostatic attraction is the main driving force at low temperature and the physical adsorption from mesopore plays a dominating role at high temperature. The introduction of amino ILs and magnetic Fe3O4 nanoparticles into mesoporous silica structures brings significant improvements in the adsorption and separation performance.