Modulating Guest Uptake in Core–Shell MOFs with Visible Light

Mutruc, Dragos; Goulet‐Hanssens, Alexis; Fairman, Sam; Wahl, Sebastian; Zimathies, Annett; Knie, Christopher; Hecht, Stefan

doi:10.1002/anie.201906606

Cited by 91 publications

(75 citation statements)

References 31 publications

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“…We would like to note that in many of previous feasibility studies on photoactive MOF materials, the materials and switching processes were often not sufficiently well characterized. For example, the PSS of photoswitchable MOFs in the form of powder and thin films were quantified only in a few cases, e.g., by NMR, chromatography, or by infrared spectroscopy, while in most studies this important information was not determined. A precise material characterization and a detailed understanding of the MOF material and the switching processes are not only interesting for academic reasons and out of scientific curiosity but also are fundamental for device performance improvements.…”

Section: Discussionmentioning

confidence: 99%

“…A powder MOF equivalent, a core–shell MOF with UiO‐68 MOF structure, has been prepared by Hecht and co‐worker. In this case, the photoswitchable moieties were incorporated by linker exchange in the outer MOF shell . Wang and co‐workers used an Azo‐UiO‐68 MOF powder with a cyclodextrin capping blocking the pore entrances …”

Section: Photoswitchable Mofs From Photochromic Moleculesmentioning

confidence: 99%

“…The authors attributed the release of the embedded molecules to the energy absorption and the toggle motion of the AB groups. Hecht and co‐workers used UiO‐68‐MOFs with a core–shell structure (see above) to demonstrate optical control of uptake and release of pyrenecarboxylic acid in ethanol …”

Section: Photoswitchable Mofs From Photochromic Moleculesmentioning

confidence: 99%

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Advanced Photoresponsive Materials Using the Metal–Organic Framework Approach

2019

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In recent years, a particularly attractive and novel strategy has become available for the fabrication of photoresponsive, porous, and crystalline molecular solids from appropriately functionalized chromophoric linkers. The crystallinity of these materials allows a rather straightforward description and analysis using theoretical methods, thus tremendously accelerating the design of novel materials. This new class of crystalline molecular solids is referred to as metal-organic frameworks, MOFs (or porous coordination polymers, PCPs). [1] MOFs are constructed from metal-/metal-oxo nodes and organic linkers (Figure 1). The incorporation of photoactive species into MOFs may be realized by using them as linkers (method L) or attaching them to a linker (method A), as shown in Figure 1a. In addition, the porosity of MOFs allows the loading of chromophoric compounds as guests (method G) into the pores of this interesting framework material.In this review article, we mainly focus on organic photoactive species, which are either simply loaded as guests into porous MOFs or used after appropriate functionalization as building blocks for the construction of the framework (methods L, A, and G). [2] It is important to note that in the context of photoresponsive behavior, MOFs carry a potential which by far exceeds that of nonporous coordination polymers. This is because simple loading of guest/solvent molecules of different size/polarity/functionality in the MOF pores can impart a large optical response, which is useful, e.g., for sensing applications. [3] As an example, the solvent-dependent optical response or solvatochromism [4] is illustrated in Figure 1b. Such effects cannot be realized for nonporous coordination polymers.The different types of photoresponsive molecules addressed in this review can be grouped into two classes. The first contains molecules where the structure remains essentially unchanged upon light-induced electronic excitation, and the second contains molecular species that change their structure or conformation upon absorption of photons (molecular switches).Light with a wavelength in the range 200-800 nm (6.2-1.5 eV) can excite a molecule to a transient excited electronic state. The transient state then decays to a low-energy state, either the parent ground state or another longer-lived excited state. Decay time scales are in the range 10 −12 -10 1 s, and the released energy can be radiative or nonradiative in nature. For many applications, nonradiative energy loss is unwanted, When fabricating macroscopic devices exploiting the properties of organic chromophores, the corresponding molecules need to be condensed into a solid material. Since optical absorption properties are often strongly affected by interchromophore interactions, solids with a well-defined structure carry substantial advantages over amorphous materials. Here, the metal-organic framework (MOF)-based approach is presented. By appropriate functionalization, most organic chromophores can be converted to function as linkers, which can coo...

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Section: Discussionmentioning

confidence: 99%

Section: Photoswitchable Mofs From Photochromic Moleculesmentioning

confidence: 99%

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Advanced Photoresponsive Materials Using the Metal–Organic Framework Approach

2019

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“…In a somewhat related approach, the surface of MOF crystals can be functionalized with photoresponsive moieties by a process called solvent assisted ligand exchange, in which nonfunctionalized ligand molecules of the outer shell are slowly replaced by AB‐bearing linkers in solution. Thereby, well‐defined zirconium MOFs with perfect octahedral shape were formed with a thin layer consisting of linkers carrying two tetra ‐ ortho ‐fluorinated AB units ( Figure ) . This design provides remarkable photochemical performance since the ABs, implemented in the MOF structure, can be operated with visible light in both switching directions without fatigue over several switching cycles and with high photoconversions that do not deviate from the free AB units studied in dilute solution.…”

Section: Light‐responsive Porous Crystalline Materialsmentioning

confidence: 99%

“…c) Uptake experiment of 1‐pyrenecarboxylic acid followed by UV–vis spectroscopy, showing an enhanced uptake capability for the open shell layer with azobenzene moieties in the Z configuration. a–c) Adapted with permission . Copyright 2019, Wiley‐VCH.…”

Section: Light‐responsive Porous Crystalline Materialsmentioning

confidence: 99%

Enlightening Materials with Photoswitches

2020

Self Cite

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reversible conversion between their stable and (meta)stable isomers triggered by light. The return to their native, thermo dynamically most stable isomer is gener ally induced by using another wavelength of light or simply by heat, depending on the thermal stability of the (meta)stable isomer. Retinal-the prototypical photo switch in biology-showcases impressively how structural changes occurring during a lightinduced doublebond isomerization can lead to vision or allow microorganisms to convert photons into metabolic energy. In analogy, over the years, scientists have learned that the lightdriven isomeriza tion of small molecules can be collected, possibly amplified, and transformed into macroscopic property changes, such as mechanical motion, [1] charge carrying ability, [2] assembly and disassembly of macroscopic aggregates, [3] as well as switching of surfaces and their properties. [4] Materials, which for the purpose of this review are consid ered to be solid objects or organized assemblies in solution, provide unique advantages to enhance the function of photo switches and even create new functions when compared to their standalone molecular selves (for the primarily discussed photochromic molecules herein, see Figure 1). One must, how ever, consider the inherent challenges that may present them selves when working with photoswitches in close proximity to one another. Intermolecular interactions, such as aggregation, excitation quenching, low freevolume, as well as the poten tially much higher optical density of materials can drastically lower the overall photoresponse. Yet with proper macromo lecular and supramolecular design, functions can be achieved through the incorporation of photoswitches in a material that simply cannot be obtained by an isolated molecule on its own. Here, we highlight recent examples from the literature that have appeared during the past decade since our previous review in this journal, [5] with particular focus on the order of the photos witches in relation to their environment and its impact on mate rial properties and device performance.Conceptually, one can think about maximizing a photo switching unit's effect by giving it "order" with relation to its surrounding, in particular to other switching units (Figure 2). The lowest possible order is undoubtedly demonstrated by dis persing photochromic molecules in a bulk amorphous material. If aggregation of the photoswitches can be overcome, switching units are placed in random orientation to each other giving rise to a more or less isotropic material. Starting from this scenario of randomly distributed photochromic entities, one can think about providing order in two dimensions by placing Incorporating molecular photoswitches into various materials provides unique opportunities for controlling their properties and functions with high spatiotemporal resolution using remote optical stimuli. The great and largely still untapped potential of these photoresponsive systems has not yet been fully exploited due to the fundamental challenge...

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Assembly of Molecular Building Blocks into Integrated Complex Functional Molecular Systems: Structuring Matter Made to Order

Hassan

Matt

Begum³

et al. 2020

Adv Funct Materials

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Function‐inspired design of molecular building blocks for their assembly into complex systems has been an objective in engineering nanostructures and materials modulation at nanoscale. This article summarizes recent research and inspiring progress in the design/synthesis of various custom‐made chiral, switchable, and highly responsive molecular building blocks for the construction of diverse covalent/noncovalent assemblies with tailored topologies, properties, and functions. Illustrating the judicious selection of building blocks, orthogonal functionalities, and innate physical/chemical properties that bring diversity and complex functions once reticulated into materials, special focus is given to their assembly into porous crystalline networks such as metal/covalent–organic frameworks (MOFs/COFs), surface‐mounted frameworks (SURMOFs), metal–organic cages/rings (MOCs), cross‐linked polymer gels, porous organic polymers (POPs), and related architectures that find diverse applications in life science and various other functional materials. Smart and stimuli‐responsive or dynamic building blocks, once embedded into materials, can be remotely modulated by external stimuli (light, electrons, chemicals, or mechanical forces) for controlling the structure and properties, thus being applicable for dynamic photochemical and mechanochemical control in constructing new forms of matter made to order. Then, an overview of current challenges, limitations, as well as future research directions and opportunities in this field, are discussed.

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Modulating Guest Uptake in Core–Shell MOFs with Visible Light

Cited by 91 publications

References 31 publications

Advanced Photoresponsive Materials Using the Metal–Organic Framework Approach

Advanced Photoresponsive Materials Using the Metal–Organic Framework Approach

Enlightening Materials with Photoswitches

Assembly of Molecular Building Blocks into Integrated Complex Functional Molecular Systems: Structuring Matter Made to Order

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