Rigid molecular sieving materials work well for small molecules with the complete exclusion of large ones1,2,3, and molecules with matching physiochemical properties may be separated using dynamic molecular sieving materials4,5,6. Metal–organic frameworks (MOFs)7,8,9 are known for their precise control of structures and functions on a molecular level10,11,12,13,14,15. However, the rational design of local flexibility in the MOF framework for dynamic molecular sieving remains difficult and challenging. Here we report a MOF material (JNU-3a) featuring one-dimension channels with embedded molecular pockets opening to propylene (C3H6) and propane (C3H8) at substantially different pressures. The dynamic nature of the pockets is revealed by single-crystal-to-single-crystal transformation upon exposure of JNU-3a to an atmosphere of C3H6 or C3H8. Breakthrough experiments demonstrate that JNU-3a can realize high-purity C3H6 (≥99.5%) in a single adsorption–desorption cycle from an equimolar C3H6/C3H8 mixture over a broad range of flow rates, with a maximum C3H6 productivity of 53.5 litres per kilogram. The underlying separation mechanism—orthogonal-array dynamic molecular sieving—enables both large separation capacity and fast adsorption–desorption kinetics. This work presents a next-generation sieving material design that has potential for applications in adsorptive separation.
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The data that support the plots within this paper and other finding of this study are available from the corresponding authors upon reasonable request. The X-ray crystallographic coordinates for structures reported in this Article have been deposited at the Cambridge Crystallographic Data Centre (CCDC), under deposition numbers CCDC 2018163–2018167. These data can be obtained free of charge from the Cambridge Crystallographic Data Centre via https://www.ccdc.cam.ac.uk/data_request/cif.
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We thank W. Chen and A. Zheng from the Wuhan Institute of Physics and Mathematics (WIPM) of Chinese Academy of Sciences for their advice on computational studies. This work was financially supported by the National Natural Science Foundation of China (nos 21731002 and 21975104), the Guangdong Major Project of Basic and Applied Research (no. 2019B030302009), and Guangdong Basic and Applied Basic Research Foundation (no. 2020A1515011005).
The authors declare no competing interests.
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Extended data figures and tables
Local coordination environment of Co2+. Co, light blue; C, dark grey; N, blue; O, red; H, white.
Connolly surface representation of JNU-3a viewed along the a axis (yellow/grey curved surface).
a–d, Differential scanning calorimetry of 50/50 mixed-component of C3H6/He (a), C3H8/He (b), C3H6/C3H8 (c), and helium (d) on JNU-3a at 303 K. The flow rate is 5.0 ml min−1.
Calculated IAST adsorption selectivity of C3H6 over C3H8 on JNU-3a for an equimolar mixture of C3H6/C3H8 at 303 K. P, pressure.
a, C3H6 kinetic adsorption on JNU-3a, Y-abtc and KAUST-7 at 303 K. b, C3H6 kinetic desorption on JNU-3a, Y-abtc and KAUST-7 at 303 K.
a–c, The calculated C3H6 diffusion rate constants on JNU-3a (a), KAUST-7 (b), and Y-abtc (c), fitted automatically with BEL-Master software according to the Crank theory. C, concentration; C0, initial concentration; Ce, concentration at equilibrium.
a, Geometry optimization by DFT for (i) JNU-3a@2C3H6 with fully relaxed geometry and cell parameters; and (ii) JNU-3a@2C3H6′ (the prime symbol is used here to differentiate it from scenario (i)) with fixed geometry and cell parameters. b, The rotation of the dihedral angle of the pyridine plane and triazole plane. Light blue, red, blue, white and grey represent Co, O, N, H and C atoms, respectively. H atoms are omitted in a for clarity.
Comparison of C3H6 productivity and purity estimated from the experimental breakthrough data of an equimolar C3H6/C3H8 mixture on JNU-3a, KAUST-7 and Y-abtc at different flow rates.
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Zeng, H., Xie, M., Wang, T. et al. Orthogonal-array dynamic molecular sieving of propylene/propane mixtures. Nature 595, 542–548 (2021). https://doi.org/10.1038/s41586-021-03627-8