Molecular Simulation Study on Catenation Effects on Hydrogen Uptake Capacity of MOFs
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0971-Z06-03
Molecular Simulation Study on Catenation Effects on Hydrogen Uptake Capacity of MOFs Dong Hyun Jung1, Tae Bum Lee1, Daejin Kim1, Kangsung Park1, Jaheon Kim2, and Seung-Hoon Choi1 1 Center for R&D, Insilicotech Co. Ltd., A-1101, Kolontripolis, 210, Geumgok-Dong, BundangGu, Seongnam-Shi, 463-943, Korea, Republic of 2 Department of Chemistry, Soongsil University, 1-1, Sangdo-5-Dong, Dongjak-Gu, Seoul, 156743, Korea, Republic of
ABSTRACT In order to investigate the reason for the higher capacity of the interpenetrating isoreticular metal-organic frameworks (IRMOFs) at lower temperatures, we performed grand canonical Monte Carlo (GCMC) simulations and molecular dynamics simulations at 77 K for a set of the interpenetrating IRMOF-11 and the non-interpenetrating counterpart IRMOF-12. From the GCMC simulations, we found universal force field (UFF) is better for describing the hydrogen adsorption behavior than DREIDING force field. The results from the molecular dynamics simulations showed the density of adsorbed hydrogen molecules was increased in the various pores created by the catenation of IRMOF comparing to that of the pores in IRMOF-12. Moreover, the adsorbed hydrogen molecules in IRMOF-11 have the smaller diffusion coefficients. It means that their dynamic behavior is more restricted because of the complexity of the interpenetrating network of IRMOF-11. These results of molecular simulations show the small pores created by the catenation are important for the increase of hydrogen adsorption on IRMOF-11 at lower temperatures. INTRODUCTION Yaghi et al. showed that catenation of isoreticular metal-organic framework (IRMOF) chains may be one of the candidate methods to improve hydrogen capacity at 77 K [1]. The framework catenation is a unique property of MOFs that are not usually observed in zeolites. Many small pores are made by catenation in IRMOFs, and these small and more compact pores are suggested to be related with its increased capacity, but due to the limitation of experimental analysis, the direct evidence was not presented yet. In our recent studies [2-5], a mechanism of hydrogen adsorption [2], quantitative structure-property relationship between organic linkers and hydrogen uptake [3], and hydrogen adsorption isotherm simulations using grand canonical Monte Carlo (GCMC) simulations [4, 5] were investigated. However, the dynamic behavior of the adsorbed hydrogen was not investigated in the previous studies. In this work, we select a proper force field to describe the hydrogen adsorption behavior by using GCMC simulations and the dynamic behavior of adsorbed hydrogen molecules will be explained by molecular dynamics simulations based on the selected force field.
SIMULATION MODELS AND METHODS Model systems used in this work are the non-interpenetrating IRMOF-12 and its interpenetrating counter part, IRMOF-11. IRMOF-11 and -12 have 4, 5, 9, 10-tetrahydropyrene2, 7-dicarboxylate as the organic linkers. IRMOF-11 is the interweaving network of two chains of IRMOF-12. The lattice structures of IRMOF
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