Untwisted restacking of two-dimensional metal-organic framework nanosheets for highly selective isomer separations

Ze-Rong Tao,Da-Huan Liu,Lin Gu,Ming Xu,Qing-Hua Zhang,Wen-Qi Tang,Ying-Jie Zhao,Zhi-Yuan Gu,Jian-Xiang Wu

doi:10.1038/s41467-019-10971-x

Abstract

The stacking between nanosheets is an intriguing and inevitable phenomenon in the chemistry of nano-interfaces. Two-dimensional metal-organic framework nanosheets are an emerging type of nanosheets with ultrathin and porous features, which have high potential in separation applications. Here, the stacking between single-layer metal-organic framework nanosheets is revealed to show three representative conformations with tilted angles of 8°, 14°, and 30° for Zr-1, 3, 5-(4-carboxylphenyl)-benzene framework as an example. Efficient untwisted stacking strategy by simple heating is proposed. A detailed structural analysis of stacking modes reveals the creation of highly ordered sub-nanometer micropores in the interspacing of untwisted nano-layers, yielding a high-resolution separator for the pair of para-/meta-isomers over the twisted counterparts and commercial HP-5MS and VF-WAXMS columns. This general method is proven by additional nanosheet examples and supported by Grand Canonical Monte Carlo simulation. This finding will provide a synthetic route in the rational design of functionalities in two-dimensional metal-organic framework nanosheet.

Highlights

The stacking between nanosheets is an intriguing and inevitable phenomenon in the chemistry of nano-interfaces
The first fabrication of MOF nanosheets-coated gas chromatographic (GC) capillary columns is achieved to show that untwisted restacking greatly enhances the separation efficiency, superior to twisted stacking nanosheets and much better even than the commercial HP-5MS and VF-WAXMS columns for para/meta isomer separation (Fig. 1c)
The ultrathin 2-D Zr-BTBFA nanosheets with 6-connected Zr6 clusters and 3-connected BTB ligands were successfully synthesized

Summary

Introduction

The stacking between nanosheets is an intriguing and inevitable phenomenon in the chemistry of nano-interfaces. To distinguish the different layers stacking between twisted and untwisted Zr-BTB-FA nanosheets, we rationalized structure by combining several pieces of information provided from PXRD, N2 isothermal adsorption, AFM, DRIFTS, and molecular simulation.

Results

Conclusion