Ionic Liquid Control The Topology And Microstructure Of Three-Dimensional Covalent Organic Framework Materials

Covalent organic frameworks?COFs?have exhibited excellent properties such as designable periodic structure,low density,high specific surface area,permanent porosity,good thermal stability,and easy functionalization and modification.As such,COFs have attracted much attention over years and have been widely used in many fields,including adsorption and separation,optoelectronics,semiconductors,catalysis,biology,proton conductivity,etc.Due to the advantages of ionic liquids in the synthesis of COFs,we attemped to synthesize 3D COFs by using ionic liquids as solvents in this dissertation and obtained COF-320-S-IL with a 3-fold interpenetrated structure via an ionic liquid interface method.Besides,3D COFs,i.e.COF-300-IL and COF-320-IL have also been synthesized under ionothermal synthesis conditons.It is of great significance to further develop the ionothermal synthesis method for COFs preparation.?1?COF-300-IL and COF-320-IL have been successfully prepared under ionothermal systhesis conditions by using tetrakis?4-aminophenyl?methane and terephthalaldehyde,4,4?-biphenyldialdehyde as the building blocks.Scanning electron microscopy?SEM?images revealed that the as-synthesized COF-300-IL and COF-320-IL showed elongated fries-like microcrystalline structure.Experimental result and theoretical simulation indicate that there are strong hydrogen bond interactions between acetic acid and Bmim NTf₂,which promotes the covalent bond interaction between the linkers.At the same time,Bmim NTf₂ acts as a structure-directing agent in the reaction system,which directs the growth of the materials along its preferred growth crystal facet.Our results show that the ionothermal synthesis method can be used as a universal method for the synthesis of3D COFs.?2?Using tetra?4-aminophenyl?methane and 4,4?-biphenyldialdehyde as building blocks,dia-c3 COF-320-S-IL has been prepared by an ionic liquid interface method.Compared to the conventional solvothermal synthesis where COF-320-S with a 9-fold interpenetrated structure and rice grain microcrystalline morphology,was obtained,COF-320-S-IL material exhibited a 3-fold interpenetrated?dia-c3?stubby cuboid crystallite?The size of COF-320-S-IL reaches 0.8×0.8×2.0?m?and the specific surface area reaches up to 2201 cm² g^–1.The results show that through the ionic liquid interface synthesis method,COF-320 materials with lower interpenetration can be obtained,which is more beneficial for molecular transmission.