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

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.

Separation and Purification of Hydrocarbons with Porous Materials

“…[109] Functionalized Zr‐BTB nanosheets with an untwisted stacking mode were examined for chromatographic separation. [110] The stacking was untwisted and ordered sub‐nanometer pores were created by preheating; a column coated with the untwisted nanosheets exhibited practical PX selectivity from xylene isomers. In 2018, Long et al.…”

Conductive metal‐organic frameworks: Recent advances in electrochemical energy‐related applications and perspectives

“…Anyway, some MOFs are still obtained at higher synthesis temperature. For example, 2D Zr‐BTB nanosheets (NSs) (BTB = 1,3,5‐(4‐carboxyphenyl)‐benzene) are synthesized by dissolving H 3 BTB and ZrCl 4 in N,N ‐dimethylformamide (DMF), and then reacting at 120°C for 48 hours after the addition of formic acid and H 2 O 44 . The zirconium‐based UiO‐66‐X (X = H, NH 2 , and N + (CH 3 ) 3 ) is fabricated through the solvothermal process at 100°C 42 .…”

“…For example, 2D Zr-BTB nanosheets (NSs) (BTB = 1,3,5-(4-carboxyphenyl)-benzene) are synthesized by dissolving H 3 BTB and ZrCl 4 in N,N-dimethylformamide (DMF), and then reacting at 120°C for 48 hours after the addition of formic acid and H 2 O. 44 The zirconium-based UiO-66-X (X = H, NH 2 , and N + (CH 3 ) 3 ) is fabricated through the solvothermal process at 100°C. 42 Besides, the 3,9,10,16,17,23,24-octahydroxy pht halocyaninato)Fe]) is also synthesized by dissolving PcFe-OH 8 , iron acetate, and potassium acetate in the mixed solution of N-methyl-2-pyrrolidone (NMP)/H 2 O at 150°C.…”

Horizontal Restacking Control of Covalent Organic Framework Nanosheets for Ultrathin Gas Separation Membranes

“…In fact, similar shift in PXRD was observed in the twisted and untwisted restacking of 2D MOF nanosheets in our recent work. 40 In Raman spectroscopy (Figure 4 B), the value of I D /I G is increased from 1.61 to 1.72 with the change of preparation temperature (from 293 K to 453 K), suggesting a less organized carbon structure. 41 In consideration of the same thickness of membrane, the differences in PXRD and Raman spectra may be due to the change of the relative position of restacked nanosheets in the horizontal direction along the surface of support, caused by thermal perturbation using different temperatures.…”