Synthesis and simulation of porous organic cages



Jiang, Shan
Synthesis and simulation of porous organic cages. [Unspecified]

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Abstract

The design of porous organic molecules in the solid state where packing is dictated by weak van der Waals forces is attracting considerable attention. Most organic molecules pack in such a way to minimize free volume, which suggests molecules with permanent porosity in the solid state is rare. In this thesis, an experimental and molecular modeling study of porous organic cages is presented. These porous cage molecules are of interest for a wide range of applications in gas storage, separation and molecular recognition. Compared with other classes of porous materials such as porous frameworks or porous polymers, porous organic molecules possess potential advantages in solubility, molecular mobility and synthetic diversity. A series of tetrahedral imine linked cage molecules can be synthesized by [4+6] cycloimination condensation reaction. The crystalline packing motifs of them can be directed by the vertex functionality giving control over the pore connectivity. The synthesis and characterization of one such cage molecule (CC2) is introduced in Chapter 2. The packing of the CC2 molecules is frustrated by six vertex methyl groups, leading to 1D extrinsic pore channels and isolated intrinsic voids. CC2 adsorbs a number of gases such as N2, H2, CO2 and CH4. The H2 adsorption capacity of this material exceeds reports for other porous organic molecules. In addition, a ‘propeller’ shaped crystalline porous organic cage molecule, CC6, is prepared by [2+3] cycloimination reaction (Chapter 3). The cage molecule has a compact structure with a little void inside the cage. A narrow 1D channel is formed by molecular ineffective packing. The material demonstrates selective adsorption of H2 and CO2 over N2. We have found these cage molecules can inefficiently pack, creating permanent porosity in the amorphous solid state. These scrambled cage molecules are synthesized by either dynamic exchange reactions or co-reactions (Chapter 5). They show a high level of porosity and H2/N2 gas selectivity can be tuned by varying the cage functionality. The BET surface area of up to 898 m2 g-1 exceeds comparable amorphous molecular solids. A methodology is designed to generate amorphous cage structural models and gas diffusion simulations are also performed for these materials in Chapter 6. The simulations provide detailed information of the microscopic structures in these amorphous materials, including gas hopping, accumulative cage occupancy by gas molecules, residential times, and diffusion pathways, which cannot be achieved by experimental techniques.

Item Type: Unspecified
Additional Information: Date: 2012 (completed)
Uncontrolled Keywords: Porous organic cages, gas storage, gas separation, amorphous porous materials, gas diffusion analysis, Molecular Dynamic simulation for amorphous porous materials, Porosity
Subjects: Q Science > QD Chemistry
Divisions: ?? dep_chem ??
Depositing User: Symplectic Admin
Date Deposited: 15 Aug 2013 11:15
Last Modified: 09 Jan 2021 08:56
URI: https://livrepository.liverpool.ac.uk/id/eprint/8013