Solid State NMR Studies Of Host-guest Interaction Between Light Alkanes And UiO-67

Metal-organic frameworks?MOFs?are attractive porous materials having a widely application in gas storage,separation,catalysis and many other important fields,due to their excellent porous structures and high specific surface area.Recently,tremendous efforts have been made to design new MOF materials to storage clean desirable fuel gas and separate chemical materials.Accordingly,it is of great significance to explore the host-guest interaction mechanism in MOFs to correlate the structure-property relationship.In this dissertation,research progress regarding solid state NMR studies of the host-guest interaction between light alkanes,aromatic hydrocarbon and MOFs has been achieved and described as following.?1?Solid-state NMR spectroscopy was employed to explore the host-guest interactions between light alkanes including methane,ethane,propane and UiO-67 at room temperature.The existence of host-guest interaction between light alkanes and UiO-67 framework is clearly evidenced from two-dimensional ¹H-¹H EXSY and ¹H-¹³C HETCOR with spin diffusion experiments.By fitting the spin diffusion buildup curves,it is found that methane is more readily to diffuse to the UiO-67 framework compared to ethane and propane.Moreover,the spin diffusion MAS NMR results reveal that methane is mainly adsorbed on the metal cluster,whereas propane is preferentially present nearby the proton site away from the metal cluster due to the steric hindrance effect.This work will contribute to a better understanding of the structure-property relationship in the alkane storage of MOFs.?2?Solid state NMR was employed to propose the separation mechanism for styrene?St?compared to ethylbenzene?EB?in MIL-53.Firstly,¹H,¹³C and ²⁷Al NMR experiments were used to assess the distinct influences to the MIL-53 structure upon introduction of St in comparison with EB.Stronger host-guest interaction between St compared to EB and MIL-53 framework has been evidenced from the¹³C-²⁷Al RESPDOR NMR experiments.Additionally,¹³C DIPSHIFT NMR experimental results confirm that the St molecule confined inside the MIL-53 pore is less mobile due to presence of?-?interaction.The host-guest interaction models between St compared to EB and MIL-53are proposed according to a series of ¹H DQ MAS NMR and ¹H-¹H EXSY NMR spectra.Thus,it was correlated the structure-property relationship for the separation of St and EB using MIL-53 and the presence of host-guest interaction during application process.