Polymer membranes are widely used in separation processes including desalination1, organic solvent nanofiltration2,3 and crude oil fractionation4,5. Nevertheless, direct evidence of subnanometre pores and a feasible method of manipulating their size is still challenging because of the molecular fluctuations of poorly defined voids in polymers6. Macrocycles with intrinsic cavities could potentially tackle this challenge. However, unfunctionalized macrocycles with indistinguishable reactivities tend towards disordered packing in films hundreds of nanometres thick7,8,9, hindering cavity interconnection and formation of through-pores. Here, we synthesized selectively functionalized macrocycles with differentiated reactivities that preferentially aligned to create well-defined pores across an ultrathin nanofilm. The ordered structure was enhanced by reducing the nanofilm thickness down to several nanometres. This orientated architecture enabled direct visualization of subnanometre macrocycle pores in the nanofilm surfaces, with the size tailored to ångström precision by varying the macrocycle identity. Aligned macrocycle membranes provided twice the methanol permeance and higher selectivity compared to disordered counterparts. Used in high-value separations, exemplified here by enriching cannabidiol oil, they achieved one order of magnitude faster ethanol transport and threefold higher enrichment than commercial state-of-the-art membranes. This approach offers a feasible strategy for creating subnanometre channels in polymer membranes, and demonstrates their potential for accurate molecular separations.
Bibliographical noteKAUST Repository Item: Exported on 2022-09-14
Acknowledged KAUST grant number(s): OSR-2017-CRG6-3441.01
Acknowledgements: Z.J. acknowledges support from Engineering and Physical Sciences Research Council (grant no. CBET-EPSRC EP/R018847). M.A.E. and S.L. acknowledge support from the King Abdullah University of Science and Technology Office of Sponsored Research under award no. OSR-2017-CRG6-3441.01. A.G.L. acknowledges support from the European Research Council, Advanced grant no. 786398. D.A. and N.B. acknowledge support from the Deutsche Forschungsgemeinschaft (grant no. AN 370/8-1) and from the European Union’s Horizon 2020 research and innovation programme under grant agreement no. 899528. A.M.E. acknowledges support from the National Science Foundation Graduate Research Fellowship under grant no. DGE-1324585.
This publication acknowledges KAUST support, but has no KAUST affiliated authors.
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