Molecular Simulation Study Of Methane Storage In Metal-Organic Frameworks And Synthesis Of MOF-5

Metal-Organic Frameworks (MOFs), commonly recognized as "soft" analogues of zeolites, is a new class of nanoporous materials. MOFs, with extremely high porosity, chemical diversity, and as tailored materials with well-defined pore size, 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 methane storage in MOFs using molecular simulation technique, and the new material was designed by investigating the adsorption mechanism in MOFs. Furthermore, we also synthesized a MOF material named MOF-5. The main contents and findings are summarized as follows:(1) An effective method denoted as "center of mass probability distributions" was employed to study the methane adsorption mechanism in metal-organic framework PCN-14 which shows the highest methane storage capacity to date, finding that this material has two adsorption sites for methane molecules, and the organic linkers play an important role in adsorption.(2) Based on this point, two new materials named PCN-M1 and PCN-M2 were designed by modifying the organic linkers of PCN-14. The newly designed MOF materials have a methane storage capacity of ca. 246 and 257 v/v at 290 K and 3.5 MPa, which is 7 % and 12 % higher than that of PCN-14. On the other hand, it has a methane capacity of ca. 241 v/v at 298 K and 3.5 MPa in PCN-M2, which is 34 % over the DOE target (180 v/v).(3) In order to further verify the simulation results mentioned above, we should experimentally synthesize the new designed materials and investigate their structural characteristics, as well as the adsorption performance. Thus, we can develop a higher amount of methane stored MOF materials. However, as the limited ability in synthesis of MOF materials in our laboratory, we have to synthesize a relatively simple material (MOF-5) firstly, as the preliminary exploration work.