In this Review, we showcase the upsurge in the development and fundamental photophysical studies of more than 100 metal−organic frameworks (MOFs) as versatile stimuli-responsive platforms. The goal is to provide a comprehensive analysis of the field of photoresponsive MOFs while delving into the underlying photophysical properties of various classes of photochromic molecules including diarylethene, azobenzene, and spiropyran as well as naphthalenediimide and viologen derivatives integrated inside a MOF matrix as part of a framework backbone, as a ligand side group, or as a guest. In particular, the geometrical constraints, photoisomerization rates, and electronic structures of photochromic molecules integrated inside a rigid MOF scaffold are discussed. Thus, this Review reflects on the challenges and opportunities of using photoswitchable MOFs in next-generation multifunctional stimuli-responsive materials while highlighting their use in optoelectronics, erasable inks, or as the next generation of sensing devices. CONTENTS1. Introduction 8790 2. Photoresponsive Moieties as a Framework Backbone 8791 2.1. Diarylethene Derivatives as a Framework Backbone 8797 2.2. Viologen Derivatives as a Framework Backbone 8799 2.3. Naphthalenediimide Derivatives as a Framework Backbone 8801 3. Photoresponsive Moiety as a Ligand Side Group 8801 3.1. Azobenzene Moiety as a Linker Side Group 8801 3.2. Diarylethene Moiety as a Linker Side Group 8803 3.3. Spiropyran Moiety as a Linker Side Group 8803 3.4. Viologen Moiety as a Linker Side Group 8804 4. Photochromic Compound as a Guest 8804 4.1. Azobenzene as a Guest 8804 4.2. Diarylethene as a Guest 8805 4.3. Spiropyran as a Guest 8805 4.4. Viologen as a Guest 8805 4.5.

Electronic structure modulation of metal–organic frameworks (MOFs) through the connection of linker “wires” as a function of an external stimulus is reported for the first time. The established correlation between MOF electronic properties and photoisomerization kinetics as well as changes in an absorption profile is unprecedented for extended well-defined structures containing coordinatively integrated photoresponsive linkers. The presented studies were carried out on both single crystal and bulk powder with preservation of framework integrity. An LED-containing electric circuit, in which the switching behavior was driven by the changes in MOF electronic profile, was built for visualization of experimental findings. The demonstrated concept could be used as a blueprint for development of stimuli-responsive materials with dynamically controlled electronic behavior.

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For the first time, we report the ability to control radionuclide species release kinetics in metal–organic frameworks (MOFs) as a function of postsynthetic capping linker installation, which is essential for understanding MOF potential as viable radionuclide wasteform materials or versatile platforms for sensing, leaching, and radionuclide sequestration. The radiation damage of prepared frameworks under γ radiation has also been studied. We envision that the presented studies are the first steps toward utilization of the reported scaffolds for more efficient nuclear waste administration.

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