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

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 4 th 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, [M 1 M 2 (2,6-ndc) 2 dabco] n , 2,6-ndc = 2,6,-naphthalene dicarboxylate, dabco = 1,4 diazabicyclo[2.2.2]octane, M 1 = Ni, M 2 = Co) is presented. The temporal response is deliberately tuned by variations in 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. Differences in the spatiotemporal response of crystal ensembles originate from an induction time that varies statistically and widens characteristically with increasing cobalt content reflecting increasing activation barriers. This article is protected by copyright. All rights reserved.