Research Article pubs.acs.org/journal/ascecg
Cite This: ACS Sustainable Chem. Eng. XXXX, XXX, XXX−XXX
Anion Pillared Metal−Organic Framework Embedded with Molecular Rotors for Size-Selective Capture of CO2 from CH4 and N2 Lifeng Yang, Xili Cui, Yuanbin Zhang, Qingju Wang, Zhaoqiang Zhang, Xian Suo, and Huabin Xing* Key Laboratory of Biomass Chemical Engineering of Ministry of Education, Department of Chemical and Biological Engineering, Zhejiang University, Hangzhou 310027, China
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ABSTRACT: The CO2 sequestration is extremely urgent due to the growing greenhouse effect and the subsequent serious environmental crisis. The development of porous materials with a size-selective effect for CO2 from other molecules still remains a challenge, due to the difficulties to control pore size within 3−4 Å. Here, we proposed and designed a novel anion-pillared material (termed as ZU-66, ZU = Zhejiang University) embedded with “molecular rotors” toward the industrially relevant CO2/ CH4 and CO2/N2 separation. Interestingly, the temporarily fixed molecular rotors under the ambient condition afforded a size-selective channel for CO2 from CH4 and N2. To our best knowledge, there were only a handful of examples achieving the molecular sieving between CO2 and CH4. Such a behavior endowed ZU-66 with high separation selectivity for both CO2/ CH4 (136) and CO2/N2 (355) and high CO2 capacity (4.56 mmol g−1, 298 K, 1 bar). The actual breakthrough experiment further verified its great potential in both CO2/CH4 and CO2/N2 separation. The specific adsorption behavior within ZU-66 was further revealed through the modeling calculation. KEYWORDS: Metal−organic frameworks, CO2 sequestration, CO2/CH4/N2 separation, Size-selective, Molecular rotor
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INTRODUCTION Carbon dioxide (CO2) sequestration to mitigate massive CO2 emissions derived from energy production and industrial process is imperative to prevent serious consequences on the environment, due to the rapidly increasing atmospheric CO2 concentration (>400 ppm).1−4 Natural gas is always mixed with CO2, which not only largely reduces the caloric value of the delivered CH4 but also triggers the danger caused by the corrosion on the transportation pipelines.5−7 Additionally, the combustion of carbon-based fossil fuels almost accounts for about 40% of the world’s anthropogenic CO2 emissions, and thus the CO2 capture from the industrial flue gas (termed postcombustion capture, 15% CO 2 , 85% N 2 ) is also urgent.8−11 Therefore, the selective capture of CO2 is of great importance for the reduction of CO2 emissions, also for the purification of natural gas and flue gas.12−17 Traditional amine scrubbing ways are limited by high energy consumption to regenerate the sorbent materials accompanied by solvent loss.18,19 Relatively, adsorption is recognized as the novel efficient way for CO2 capture, due to its low energy penalty to cover loading and regeneration process. Metal−organic frameworks (MOFs) are a revolutionary class of materials via the self-assembly of metal ions/clusters and organic ligands.20−22 And the infinite organic and inorganic chemistries enable us to design the assembled building blocks targeting for the CO2 capture.23,24 The common ways such as grafting polar functional groups,25−30 or incorporating strong binding sites,28,29 are adopted to © XXXX American Chemical Society
increase the affinity between the framework and CO 2 molecules, but with the lack of satisfactory separation selectivity.31,32 On the other hand, molecular sieving as another important separation strategy enables really high separation selectivity.33,34 However, the design of materials with molecular sieving in precisely controlled pore-size within 3−4 Å is challenging, especially to those with close molecular dimensions. Therefore, the development of an efficient way to achieve the porous materials with high CO2 separation selectivity and high CO2 capacity is of great importance.35 Molecular rotor containing porous materials can be realized by self-assembly of suitable organic or inorganic building blocks.36−38 The embedding of ordered rotary groups into the ultramicroporous (
