Photoresponsive Metal Organic Frameworks Research Articles

Enhanced photocatalytic and photothermal properties of ecofriendly metal-organic framework heterojunction for rapid sterilization

Injured tissues are susceptible to infections that suppress wound healing. Rapid and safe sterilization is therefore urgent for bacteria-infected wounds, especially under harsh conditions without antibiotic availability. In this work, we developed a photoresponsive metal–organic framework (MOF) heterojunction that responds to 660 nm light irradiation. It is composed of two kinds of MOFs (Prussian blue [PB] and PCN-224), which exhibited an enhanced photocatalytic performance due to the accelerated charge transfer of the heterojunction and the fast separation of photogenerated electron-hole pairs between PB and PCN-224. The combination of the enhanced photocatalytic performance and the intrinsic photothermal effect of PB endowed the MOFs heterojunction with highly effective sterilizing rates of 99.84% and 99.3% against Staphylococcus aureus and its biofilm after 660 nm light irradiation for 15 min, respectively. The iron and zirconium ions released from PB-PCN-224 composites were biocompatible and their cytotoxicity was negligible. More importantly, in vivo experiments showed that PB-PCN-224 can expedite wound healing.

Copper-Linked Rotaxanes for the Building of Photoresponsive Metal Organic Frameworks with Controlled Cargo Delivery.

We have prepared a photoresponsive metal-organic framework by using an amide-based [2]rotaxane as linker and copper(II) ions as metal nodes. The interlocked linker was obtained by the hydrogen bond-directed approach employing a fumaramide thread as template of the macrocyclic component, this latter incorporating two carboxyl groups. Single crystal X-ray diffraction analysis of the metal-organic framework, prepared under solvothermal conditions, showed the formation of stacked 2D rhombohedral grids forming channels decorated with the interlocked alkenyl threads. A series of metal-organic frameworks differing in the E/Z olefin ratio were prepared either by the previous isomerization of the linker or by postirradiation of the reticulated materials. By dynamic solid state 2H NMR measurements, using deuterium-labeled materials, we proved that the geometry of the olefinic axis of the interlocked struts determined the obtention of materials with different independent local dynamics as a result of the strength of the intercomponent noncovalent interactions. Moreover, the usefulness of these novel copper-rotaxane materials as molecular dosing containers has also been assayed by the diffusion and photorelease of p-benzoquinone, evaluated in different solvents and temperatures.

Computational Design of a Photoresponsive Metal–Organic Framework for Post Combustion Carbon Capture

A Mg-IRMOF-74-III structure with azopyridine molecules attached to its unsaturated metal sites is proposed as a new photoresponsive metal–organic framework (MOF) for CO2 capture. Computational simu...

Atomistic Insight Into the Host-Guest Interaction of a Photoresponsive Metal-Organic Framework.

Photoresponsive functional materials have gained increasing attention due to their externally tunable properties. Molecular switches embedded in these materials enable the control of phenomena at the atomic level by light. Metal–organic frameworks (MOFs) provide a versatile platform to immobilize these photoresponsive units within defined molecular environments to optimize the intended functionality. For the application of these photoresponsive MOFs (pho‐MOFs), it is crucial to understand the influence of the switching state on the host–guest interaction. Therefore, we present a detailed insight into the impact of molecular switching on the intermolecular interactions. By performing atomistic simulations, we revealed that due to different interactions of the guest molecules with the two isomeric states of an azobenzene‐functionalized MOF, both the adsorption sites and the orientation of the molecules within the pores are modulated. By shedding light on the host–guest interaction, our study highlights the unique potential of pho‐MOFs to tailor molecular interaction by light.

Metal-Organic Frameworks with Target-Specific Active Sites Switched by Photoresponsive Motifs: Efficient Adsorbents for Tailorable CO2 Capture.

Photoresponsive metal-organic frameworks (PMOFs) are of interest for tailorable CO2 adsorption. However, modulation of CO2 adsorption on PMOFs is based on steric hindrance or structural change owing to weak interactions between CO2 and active sites. It is challenging to fabricate PMOFs with strong but tailorable sites for CO2 adsorption. Now, the construction of PMOFs with target-specific (strong) active sites is achieved by introducing tetraethylenepentamine into azobenzene-functionalized MOFs for tailorable CO2 adsorption. Amines are specific active sites for CO2 , contributing to capture CO2 selectively. Cis/trans isomerization of azobenzene motifs trigged by UV/Vis light adjusts the electrostatic potential of amines significantly, leading to exposure/shelter of amines and modulation of CO2 adsorption on strong active sites. This system enables us to design adsorption processes for CO2 capture from mixtures, which is impossible to realize by traditional PMOFs.

Frontispiece: Tuning Gas Adsorption by Metal Node Blocking in Photoresponsive Metal–Organic Frameworks

Frontispiece: Tuning Gas Adsorption by Metal Node Blocking in Photoresponsive Metal–Organic Frameworks

Tuning Gas Adsorption by Metal Node Blocking in Photoresponsive Metal-Organic Frameworks.

By combining first-principles calculations and classical molecular simulations, an atomistic-level of understanding was provided towards the notable change in CO2 adsorption upon light treatment in two recently reported photoactive metal-organic frameworks, PCN-123 and Cu2 (AzoBPDC)2 (AzoBiPyB). It was demonstrated that the reversible decrease in gas adsorption upon isomerization can be primarily attributed to the blocking of the strong adsorbing sites at the metal nodes by azobenzene molecules in a cis configuration. The same mechanism was found to apply also to other molecules, for example, alkanes and toxic gases. Such understandings are instrumental to the future design of photoresponsive metal-organic frameworks. For example, the metal node-blocking mechanism can be leveraged to achieve optimal adsorption properties as a function of metal substitution and/or ligand functionalization. As a proof of concept, it was shown that the working capacity could be increased by a factor of two in PCN-123 by replacing the Zn4 O node with the more strongly adsorbing Mg4 O.

Reversible structural switching of a metal–organic framework by photoirradiation

A photoresponsive metal organic framework material undergoes switching of its pore volume and sorption capacity. UV irradiation of the crystals causes cyclisation within the bis-thienylcyclopentene bridging ligands, thereby altering the node positions relative to one another along the Zn-L-Zn linkages. Incorporation of conformational flexibility into the dicarboxylic acid co-ligands facilitates the change in the framework geometry enforced by photocyclisation.

The lighter side of MOFs: structurally photoresponsive metal–organic frameworks

Shedding light on the design strategies used to make structurally photoactive metal–organic frameworks.

Photoswitchable metal organic frameworks: turn on the lights and close the windows

Progress and challenges in the development of photo-responsive metal organic frameworks.

Photo-responsive MOFs: light-induced switching of porous single crystals containing a photochromic diarylethene

Herein we report the synthesis and characterization of light responsive metal organic framework (MOF) single crystals containing the photochromic diarylethene 1,2-bis(2,5-dimethyl-thien-3-yl)perfluorocyclopentene. Polarized light microscopy on single crystals indicates that the photochrome is preferentially aligned along the c-axis of the host.