Shape-Memory Effect Enabled by Ligand Substitution and CO2 Affinity in a Flexible SIFSIX Coordination Network |
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Authors: | Dr Bai-Qiao Song Dr Mohana Shivanna Dr Mei-Yan Gao Dr Shi-Qiang Wang Cheng-Hua Deng Prof Qing-Yuan Yang Dr Sousa Javan Nikkhah Prof Matthias Vandichel Prof Susumu Kitagawa Prof Michael J Zaworotko |
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Institution: | 1. College of Materials and Chemistry & Chemical Engineering, Chengdu University of Technology, 610059 Chengdu, China;2. Institute for Integrated Cell-Material Sciences, Institute for Advanced Study, Kyoto University, Ushinomiya, Yoshida, Sakyo-ku, 606-8501 Kyoto, Japan;3. Department of Chemical Sciences and Bernal Institute, University of Limerick, V94?T9PX Limerick, Republic of Ireland;4. Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), Fusionopolis Way, 138634 Singapore, Singapore;5. School of Chemical Engineering and Technology, Xi'an Jiaotong University, 710049 Xi'an, China |
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Abstract: | We report that linker ligand substitution involving just one atom induces a shape-memory effect in a flexible coordination network. Specifically, whereas SIFSIX-23-Cu, Cu(SiF6)(L)2]n, (L=1,4-bis(1-imidazolyl)benzene, SiF62?=SIFSIX) has been previously reported to exhibit reversible switching between closed and open phases, the activated phase of SIFSIX-23-CuN, Cu(SiF6)(LN)2]n (LN=2,5-bis(1-imidazolyl)pyridine), transformed to a kinetically stable porous phase with strong affinity for CO2. As-synthesized SIFSIX-23-CuN, α, transformed to less open, γ, and closed, β, phases during activation. β did not adsorb N2 (77 K), rather it reverted to α induced by CO2 at 195, 273 and 298 K. CO2 desorption resulted in α′, a shape-memory phase which subsequently exhibited type-I isotherms for N2 (77 K) and CO2 as well as strong performance for separation of CO2/N2 (15/85) at 298 K and 1 bar driven by strong binding (Qst=45–51 kJ/mol) and excellent CO2/N2 selectivity (up to 700). Interestingly, α′ reverted to β after re-solvation/desolvation. Molecular simulations and density functional theory (DFT) calculations provide insight into the properties of SIFSIX-23-CuN. |
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Keywords: | CO2 Adsorption Crystal Engineering Flexible Coordination Networks Nonporous to Porous Switching Shape-Memory |
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