Effects of functional groups for CO 2 capture using metal organic frameworks
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RESEARCH ARTICLE
Effects of functional groups for CO2 capture using metal organic frameworks Chenkai Gu1, Yang Liu2, Weizhou Wang3, Jing Liu (✉)1, Jianbo Hu1 1 State Key Laboratory of Coal Combustion, School of Energy and Power Engineering, Huazhong University of Science and Technology, Wuhan 430074, China 2 School of Chemical and Biomolecular Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0100, USA 3 Henan Key Laboratory of Function-Oriented Porous Materials, College of Chemistry and Chemical Engineering, Luoyang Normal University, Luoyang 471934, China
© Higher Education Press 2020
Abstract Metal organic frameworks (MOFs) are promising adsorbents for CO2 capture. Functional groups on organic linkers of MOFs play important roles in improving the CO2 capture ability by enhancing the CO2 sorption affinity. In this work, the functionalization effects on CO2 adsorption were systematically investigated by rationally incorporating various functional groups including –SO3H, –COOH, –NH2, –OH, –CN, –CH3 and –F into a MOF-177 template using computational methods. Asymmetries of electron density on the functionalized linkers were intensified, introducing significant enhancements of the CO2 adsorption ability of the modified MOF-177. In addition, three kinds of molecular interactions between CO2 and functional groups were analyzed and summarized in this work. Especially, our results reveal that –SO3H is the best-performing functional group for CO2 capture in MOFs, better than the widely used –NH2 or –F groups. The current study provides a novel route for future MOF modification toward CO2 capture. Keywords metal-organic frameworks, functional groups, CO2 capture, GCMC, DFT
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Introduction
Carbon dioxide (CO2) from fossil fuel combustion is one of the most important greenhouse gases which result in the global warming [1,2]. Various methods have been proposed to prevent the CO2 emission into the atmosphere, among which the CO2 capture and storage (CCS) shows
Received April 3, 2020; accepted May 19, 2020 E-mail: [email protected]
great potentials in short-term CO2 reduction [3]. There are several approaches to capture CO2 from carbon emitting sources, including amine scrubbing [4,5], membrane separation [6,7], and sorbent adsorption [8–10]. Compared to the other methods, capturing CO2 using porous sorbents is especially attractive owing to the low energy consumption, high economic benefit and easy tailoring [11–13]. Comparing with the traditional porous materials such as activated carbons and zeolites, metal organic frameworks (MOFs) show more advantages in CO2 capture due to their highly tunable structures, porosities and chemical properties [14–16]. In order to improve the CO2 capture capacities of MOFs, many approaches have been proposed. The pore chemistry adjustment can benefit CO2 capture in MOFs, which depends strongly on pore topology [17]. Besides, smaller pore size usually leads to higher overlap of potential energy between CO2 molecule and MOF, contributing to higher CO2 capture abilities. An
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