CO2 adsorption performance of functionalized metal-organic frameworks of varying topologies by molecular simulations

Abstract

The mixed linker metal-organic frameworks (MOFs) consisting of a variety of organic linkers functionalized by multiple functional groups exhibit better performance in carbon capture due to the increased surface heterogeneity. In order to explore the influence of the framework topology and mixed functionalities on the carbon capture performance, in this work, Zr-MOFs in three topologies (csq, ftw, scu) with each composed by one of the three types of linkers of different lengths were constructed, which were then functionalized by three types of functional groups (F, NH2, OCH3), respectively. Grand canonical Monte Carlo (GCMC) simulations were used to investigate CO2 adsorption performance of all created MOFs. We revealed that among the parent MOFs consisted of identical building blocks but in different topologies, ftw-MOFs exhibit the highest CO2 working capacity and CO2/N2 selectivity due to the strong affinity towards CO2. Moreover, the CO2 adsorption performance of ftw-MOFs shows obvious dependence on the pore size, consistent with their host-adsorbate interaction energy, which is not the fact for csq-MOFs and scu-MOFs. The enhanced CO2 adsorption performance upon functionalization of MOFs displays pore-size dependence as well, especially for NH2 functionalized frameworks in csq and scu, which is mostly attributed to the enhanced host-adsorbate Coulombic interaction. The proposed effects of the topology, the pore size and the functional group on CO2 adsorption performance of MOFs obtained in this study may provide meaningful insight into the rational design of high-performing MOFs for carbon capture by tuning the topology, pore size and functionality of frameworks.