High and selective capture of low-concentration CO 2 with an anion-functionalized ultramicroporous metal-organic framewo
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Published online 19 October 2020 | https://doi.org/10.1007/s40843-020-1471-0
High and selective capture of low-concentration CO2 with an anion-functionalized ultramicroporous metal-organic framework *
Zhaoqiang Zhang, Qi Ding, Jiyu Cui, Xili Cui and Huabin Xing ABSTRACT CO2 capture, especially under low-pressure range, is of significance to maintain long-duration human operation in confined spaces and decrease the CO2 corrosion and freezing effect for the liquefaction of natural gas. Herein, we for the first time report a novel anion-functionalized ZU2− 16-Co (TIFSIX-3-Co, TIFSIX=hexafluorotitanate (TiF6 ), 3=pyrazine), which exhibits one-dimensional pore channels decorated by abundant F atoms, for efficient CO2 capture at a concentration around 400–10,000 ppm. Among its isostructural MFSIX-3 (M=Si, Ti, Ge) family materials, ZU-16Co with fine-tuned pore size of 3.62 Å exhibits the highest CO2 uptake at 0.01 bar (10,000 ppm) and 1 bar (2.63 and −1 2.87 mmol g , respectively). The high CO2 capture ability of ZU-16-Co originates from the fine-tuned pore dimensions with strong F···C=O host-guest interactions and relatively large pore volumes coming from its longer coordinated Ti–F– Co distance (3.9 Å) in c direction. The excellent carbon trapping performance was further verified by dynamic breakthrough tests for CO2/N2 (1/99 and 15/85) and CO2/CH4 (50/ 50) mixtures. The adsorption and separation performances, resulting from the fine-tuned pore system with periodic arrays of exposed functionalities, demonstrate that ultramicroporous ZU-16-Co can be a promising adsorbent for low-concentration carbon capture. Keywords: carbon capture, ultramicroporous metal-organic frameworks, gas adsorption, CO2/N2 separation, natural gas purification.
INTRODUCTION Capture of carbon dioxide (CO2) is of prime importance and continues to attract intensive research interest. Re-
cently, the global climate change resulting from the emission of greenhouse gas has become increasingly severe [1–4]. Atmospheric CO2 concentration has surpassed 400 ppm on several occasions since 2013, which represents an increase of over 100 ppm since pre-industrial revolution levels [5–9]. Furthermore, the requirement for long-duration human task performance in confined spaces such as submarines, spacecrafts or under-ground citadels has made the removal of low-concentration CO2 (< 0.5%) a critical technology [8,10–13]. In particular, the capture of greenhouse gas from dilute emissions has been listed as one of seven chemical separations to change the world [14–16]. Therefore, the removal of low-concentration CO2 from air, confined spaces, and natural gas has become a growing area of research but with great challenges. Currently, the separation of CO2 from flue gas (73%–77% N2, 15%–16% CO2, as well as water, SO2 and O2) [2,17] has been widely investigated and many progresses have been made [18–20]. However, only limited studies have focused on the removal of low-concentration CO2 around 0.04%–1% (400–10,000 ppm), and it is urgent and highly desirable to design
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