Materials Chemistry

Spatiotemporal Design of the Metal-Organic Framework DUT-8(M)

Authors

Abstract

Switchable metal-organic frameworks change their structure in time and selectively open their pores adsorbing guest molecules, leading to highly selective separation, pressure amplification, sensing and actuation applications. The three-dimensional engineering of metal-organic frameworks has reached a high level of maturity, but spatiotemporal evolution opens a new perspective towards engineering materials in the 4th dimension (time) by t-axis design, in essence exploiting the deliberate tuning of activation barriers. This work demonstrates the first example in which an explicit temporal engineering of a switchable metal-organic framework (DUT-8, M1M2(ndc)2dabco, ndc = 2,6,-naphthalenedicarboxylate, dabco = 1,4 diazabicyclo[2.2.2]octane, M1 = Ni, M2 = Co) is presented. The temporal response is deliberately tuned by variation of cobalt content. We present a spectrum of advanced analytical methods for analyzing the switching kinetics stimulated by vapor adsorption using in situ time resolved techniques ranging from ensemble adsorption and advanced synchrotron X-ray diffraction experiments to individual crystal analysis. A novel analysis technique based on microscopic observation of individual crystals in a microfluidic channel reveals the lowest limit for adsorption switching reported so far. The time constants for the bulk ensembles range from 2 - 300 s. Differences in spatiotemporal response of crystal ensembles originate from a delay (induction) time that varies statistically and widens characteristically with increasing cobalt content reflecting increasing activation barriers.

Content

Thumbnail image of 2022-8-23-kaskel.pdf

Supplementary material

Thumbnail image of Video 1_DUT(Ni_Co).avi
Video1 of DUT-8(Ni-Co) Crystals
Video of DUT-8(Ni-Co) Crystals varying in substitution degree during pore opening stimulated by DCM
Thumbnail image of Video_2_DUT-8(Ni)_diluted-DCM80_10mL-min - 33 - 301.avi
Video2 of DUT-8(Ni) Crystals (80 % DCM)
Video of DUT-8(Ni) Crystals during pore opening stimulated by DCM vapor (80 %)
Thumbnail image of Video_3_DUT-8(Ni)_diluted-DCM70_10mL-min - 30 - 868.avi
Video3 of DUT-8(Ni) Crystals (70 % DCM)
Video of DUT-8(Ni) Crystals during pore opening stimulated by DCM vapor (70 %)
Thumbnail image of Video_4_DUT-8(Ni)_diluted-DCM60_10mL-min-1 - 31 - 394.avi
Video4 of DUT-8(Ni) Crystals (60 % DCM)
Video of DUT-8(Ni) Crystals during pore opening stimulated by DCM vapor (60 %)
Thumbnail image of Video_5_DUT-8(Ni)_diluted-DCM50_10mL-min-1 - 29 - 345.avi
Video5 of DUT-8(Ni) Crystals (50 % DCM)
Video of DUT-8(Ni) Crystals during pore opening stimulated by DCM vapor (50 %)
Thumbnail image of Video_6_DUT-8(Ni)_DCM_10mL-min - 25 - 76.avi
Video6 of DUT-8(Ni) Crystals (100 % DCM)
Video of DUT-8(Ni) Crystals during pore opening stimulated by DCM vapor (100 %)
Thumbnail image of 2022-8-23-kaskel_SI.pdf
Supporting Information
The supporting Information contains additional details on materials synthesis, pressure drop experiments, time resolved PXRD, and the microscopy setup for dynamic switching analysis.