Computational Chemical Study Of Fluid Adsorption In Metal-Organic Frameworks And Covalent-Organic Frameworks

Metal-Organic Frameworks (MOFs), commonly recognized as "soft" analogues of zeolites, is a new class of nanoporous materials with larger surface area and porosity, chemical diversity, good thermal stability and tailorability characteristic. Covalent-Organic Frameworks (COFs), also a new class of nanoporous materials, have an even lower density than MOFs besides many advantages of MOFs retained. MOFs and COFs are promising materials for gases storage, separation, and catalyst, etc. Computational chemistry can not only overcome the limitations of traditional methods, but also provides theoretical guidance for the design of optimal adsorbents and the determination of optimal industrial operation conditions, which also saves a lot of time for complicated experimental works. In this work, a systematic study was carried out on fluid adsorption in MOFs and COFs with quantum chemical calculation and molecular simulation technique. The main contents and findings are summarized as follows: (1) In this work, grand canonical Monte Carlo (GCMC) simulations were performed to evaluate the separation performance of covalent organic frameworks (COFs) and compared with metal-organic frameworks (MOFs) for CH4/CO2/H2 mixtures. The simulation results show that the adsorption selectivities of COFs and MOFs are similar. The electrostatic contribution of framework charges in COFs should be taken into account although it is smaller than that in MOFs. In addition, the present work shows that the ideal adsorbed solution theory (IAST) is applicable to most COFs.(2) Grand canonical Monte Carlo (GCMC) simulations were performed to evaluate the separation performance of eleven IRMOFs (IRMOF-1,-3,-6,-8,-10,-11,-12,-13,-14,-16,-18), six PCNs(PCN-6', PCN-6, PCN-9, PCN-10, PCN-11, PCN-14), seven ZIFs(ZIF-1, ZIF-3, ZIF-10, ZIF-68, ZIF-69, ZIF-71, ZIF-78) and other nine MOFs(Cu-BTC, mesoMOF-1, MOF-2, MOF-14, MOF-177, MOF-505, MOF-602, MOF-HTB') for CO2/N2 mixtures. The simulation results show that for the same class materials, IRMOF-18,ZIF-78,MOF-2 show best separation performance. In addition, open metal sites and the organic linkers play an important role in adsorption separation performance, and the findings can provide theoretical guidance for the design of optimal adsorbents.