Computational Study On Separation Performance Of Covalent Organic Frameworks And Metal-organic Frameworks And Their Composites With ILs

Metal-Organic Frameworks (MOFs) and Covalent Organic Frameworks (COFs) are both of zeolite-like nanoporous materials, owing lots of unique properties such as high pore volume and surface area, tunable functionality and designable structure. Ionic liquids (ILs) are green solvents with low volatility and high thermal stability which have positive and negative charges with the free state that makes ILs have strong electrostatic interactions. Comparing with the traditional fossil fuels, natural gas has high hydrogen-carbon ratio which makes it one of the most promising alternative energy. In the process of natural gas purification, the impurity composition like C2H6, C3H8, C4H10 and other larger molecular weight hydrocarbons should be separated to achieve more economic benefits. CO2, as the main impurity composition, can not only reduce the calorific value of natural gas but also corrode the pipeline seriously. As the same time, fossil fuels are still the main source of energy in the foreseeable future, and the large amount of CO2 produced by the burning of them severely damage the global ecologic balance. So, it's an important economic and ecological significance of the selective removal of CO2 from natural gas and flue gas.In this work, Grand canonical Monte Carlo (GCMC) simulations were performed to investigate the adsorption behavior of CH4/C2H6 and CH4/C3H8 mixture in the selected 48 COFs. Then ILs are encapsulated into nine chosen COFs with high stability, suitable pore size and high adsorption selectivity of the mixture of alkanes to investigate the properties of IL/COF composites for natural gas purification. A subset of 13 diverse materials, composed of 5 MOFs and 8 COFs, were collected from the literature. A systematic computational study was performed to study the dispersion behaviors of ILs in MOFs and COFs as well as the separation capability of the IL/MOF and IL/COF composites for CO2/N2 and CO2/CH4 mixtures. The main contents are as follows:1. The selectivities of CH4/C2H6 and CH4/C3H8 mixtures in the selected 48 COFs were investigated using GCMC simulation method in 298 K and 1 bar. It may be expected that the knowledge obtained will be beneficial to guide the design/synthesis of adsorbents with excellent performance by screening out and analyzing these COFs.2. According to the above screening, nine COFs with outstanding performance were chosen as the platform for supporting [BMIM][SCN].Then, a computational study was conducted to investigate the performance of those IL/COF composites for the selectivity of alkane mixture.3. Five MOFs and eight COFs with diverse properties were selected as supporters for ILs to investigate the dispersion behaviors of ILs in them.4. A computational study was performed to investigate the effects of IL dispersion in MOFs and COFs on the adsorption behaviors of the CO2/N2 and CO2/CH4 mixtures. It may be a guidance to design the novel adsorbents with outstanding performance.