Unravelling chromism in metal–organic frameworks

Mehlana, Gift; Bourne, Susan A.

doi:10.1039/c7ce00710h

Cited by 73 publications

(55 citation statements)

References 86 publications

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“…Due to many structural, chemical, and conceptual similarities with MOFs, photoswitchable COFs and porous organic frameworks (PAFs) are considered here. Since this is a rapidly developing field, a number of review articles are available on photoswitchable MOFs . Here, we mainly focus on the switchable material properties of the molecular solids resulting from the integration of light‐responsive molecules.…”

Section: Photoswitchable Mofs From Photochromic Moleculesmentioning

confidence: 99%

“…A straightforward method for incorporating photoswitchable molecules in MOFs is by simply embedding them as guest molecules inside the pores (Figure a), often denoted as photoswitch@MOF 101h. In this approach, the only requirement is that the MOF pores must be large enough to host the photoswitches.…”

Section: Photoswitchable Mofs From Photochromic Moleculesmentioning

confidence: 99%

“…Numerous examples of such functionalized linkers have been reported. For AB, one of the simplest cases is obtained by functionalizing one of the phenyl groups with two carboxylic acid groups in para position 101g. Of interest are also approaches where the entire photoswitch is attached to the linkers after MOF construction by so‐called postsynthetic modifications (PSM) 98a,111…”

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: Photoswitchable Mofs From Photochromic Moleculesmentioning

confidence: 99%

Section: Photoswitchable Mofs From Photochromic Moleculesmentioning

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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“…39,40 To date, highpressure studies on MOFs and CPs have uncovered unprecedented structural phase transitions 41 and intermetallic charge transfer, 42 in addition to piezochromism in 1D systems whereby increased pressure has been shown to induce changes in the coordination geometry of the metal ion. 43,44 The effect of pressure on ligand-based charge transfer characteristics, and the possibility of pressure-induced N-I transitions in donor-acceptor framework materials, however, remains largely unexplored, thus spiking our interest in investigating potential pressure-dependent changes in [(Zn(DMF)) 2 (TTFTC)(DPNI)].…”

Section: Pressure-dependent Resonance Raman Scattering Spectroscopymentioning

confidence: 99%

Probing charge transfer characteristics in a donor–acceptor metal–organic framework by Raman spectroelectrochemistry and pressure-dependence studies

Usov

Leong

Chan

et al. 2018

Phys. Chem. Chem. Phys.

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The stimuli responsive behaviour of charge transfer donor-acceptor metal-organic frameworks (MOFs) remains an understudied phenomenon which may have applications in tuneable electronic materials. We now report the modification of donor-acceptor charge transfer characteristics in a semiconducting tetrathiafulvalene-naphthalene diimide-based MOF under applied electrochemical bias and pressure. We employ a facile solid state in situ Raman spectroelectrochemical technique, applied for the first time in the characterisation of electroactive MOFs, to monitor the formation of a new complex TTFTC •+ -DPNI from a largely neutral system, upon electrochemical oxidation of the framework. In situ pressuredependent Raman spectroscopy and powder X-ray diffraction experiments performed in a diamond anvil cell revealed blue shifts in the donor and acceptor vibrational modes in addition to contractions in the unit cell which are indicative of bond shortening. This study demonstrates the utility of in situ Raman spectroscopic techniques in the characterisation of redox-active MOFs and the elucidation of their electronic behaviours.

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“…Stimuli‐responsive materials have aroused intense interest due to their potential applications in molecular devices (such as chemical switches, sensors, and memory devices) . They can tune their physical properties with the external stimulation, for instance, pressure, temperature, pH, light or X‐ray and electric/magnetic field.…”

Section: Introductionmentioning

confidence: 81%

Thermochromic Behavior of Azobenzene‐based Coordination Polymer with Reversible Breathing Process

et al. 2019

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3 L = 5-(4-Sulfophenylazo) salicylic acid), was synthesized by a simple hydrothermal method. It reveals a 2D elastic layer-structured framework, forming a three-dimensional (3D) interlinked networks driven by extensive π…π stacking interactions. Removing water molecules by heating or vacuum freeze drying, it not only shows a reversible thermo-chromism but also exhibits a selective gas absorption and breathing effect. In addition, this material exhibits skeleton stability under reversible dehydra-tion/hydration. The reversible thermochromic behaviour is mainly attributed to the change of the coordination environment of Zn 2 + ions during the dehydration/hydration process. Furthermore, the film of 1 on the polylactic acid (PLA) support displayed similar reversible thermochromic behaviour with high sensitivity (large color-change and rapid response upon cooling or heating), promoting its application in switching fibres and devices, and naked-eye colorimetric sensor in the future.[a] W.

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Unravelling chromism in metal–organic frameworks

Abstract: Chromophoric MOFs are reviewed, focussing on those which change colour on application of external stimuli such as heat, pressure, light or chemical environment.

Cited by 73 publications

References 86 publications

Advanced Photoresponsive Materials Using the Metal–Organic Framework Approach

Advanced Photoresponsive Materials Using the Metal–Organic Framework Approach

Probing charge transfer characteristics in a donor–acceptor metal–organic framework by Raman spectroelectrochemistry and pressure-dependence studies

Thermochromic Behavior of Azobenzene‐based Coordination Polymer with Reversible Breathing Process

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