Chem
Volume 5, Issue 5, 9 May 2019, Pages 1337-1350
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Article
Multivariable Sieving and Hierarchical Recognition for Organic Toxics in Nonhomogeneous Channel of MOFs

https://doi.org/10.1016/j.chempr.2019.03.024Get rights and content
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Highlights

  • Hierarchical recognition strategy established with heterogeneous channels in MOFs

  • Ultrafine regulation of aperture size from 3.2 to 7.2 Å based on MIL-140s

  • Heterogeneous electronic distribution induces various non-covalent interactions

  • Hierarchical recognition strategy shows multivariable separation for organic toxics

The Bigger Picture

Effective molecular sieves are imperative for the selective separation of toxics and have similar properties in chemistry and environmental protection. However, multivariable recognition is still a great challenge for current porous sieves because they can recognize organics on the basis of only two variables (charge and size) in water. Here, we present a hierarchical recognition strategy based on a series of heterogeneous metal-organic frameworks. Our work can not only accomplish charge- and size-based separation of charged dye mixtures by charge recognition and size sieving but also realize the isolation of a wider range of challenging toxics, such as persistent organic pollutants and pesticides, by various non-covalent interactions in heterogeneous channels. In addition, this hierarchical recognition strategy can expand the application of current molecular sieves and indicate directions for the design of biomimetic sorbents with heterogeneous channels.

Summary

Developing optimal molecular sieves, which are able to perform multivariable aqueous sieving of diverse harmful organics, is of practical significance in chemistry and environmental protection. Current porous sieves, however, can only recognize organics on the basis of two variables (charge and size), which is far from enough because of the multi-complexity of the toxics. Herein, we report a series of isostructural metal-organic frameworks, MIL-140s [ZrO(O2C–R–CO2)], with triangular hydrophobic channels for the separation of dyes and practical toxics, such as high carcinogenic pesticides and persistent organic pollutants. Theoretical calculations demonstrate the key role of nonhomogeneous electron distribution within channels for recognition of various guest molecules. Multivariable sieving for both dyes and practical toxics has been validated by both separation experiments and DFT calculation. The sieving mechanisms are revealed through presenting an outside-in theoretical model, hierarchical recognition, by the regulation of surface charge, pore size, and potential energy surface of MIL-140s.

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Keywords

multivariable sieving
hierarchical recognition
heterogeneous channels
metal-organic frameworks

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These authors contributed equally

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