Photoswitchable nanoporous films by loading azobenzene in metal–organic frameworks of type HKUST-1

Abstract

Photoswitchable metal-organic frameworks (MOFs) enable the dynamic remote control of their key properties. Here, a readily producible approach is presented where photochromic molecules, i.e. azobenzene (AB) and o-tetrafluoroazobenzene (tfAB), are loaded in MOF films of type HKUST-1. These nanoporous films, which can be reversibly switched with UV/visible or only visible light, have remote-controllable guest uptake properties.

Metal‐Organic Frameworks as Hosts for Fluorinated Azobenzenes: A Path towards Quantitative Photoswitching with Visible Light

“…Compared with attempts to incorporate the photoactive functionality as a part of the backbone or a substituent of the linker used to construct the respective MOF, the approach to embed the photochromic molecule as a guest in the MOF framework has the advantage of an easy synthetic accessibility, as well as a very high versatility with respect to the MOF and the guest. One might object that the guest molecules are only weakly bonded to the MOF framework so that the thermal stability of the resulting guest@MOF systems is not high, but for azobenzene embedded in thin films of type HKUST‐1 it was shown that when stored at room temperature the guest leaves the MOF very slowly with a depletion (or desorption) time constant τ ≈360 days . However, when stored at 60 °C τ decreases significantly to 14.5 days .…”

“…The crystal structures of E ‐ and Z ‐ tF ‐AZB were reported quite recently and compared with those of the other azobenzenes depicted in Scheme and 2 . For thin (SURMOF) films of type HKUST‐1 the successful incorporation of tF ‐AZB was already proven …”

Novel Photoactive Spirooxazine Based Switch@MOF Composite Materials

“…The synthesis and design of functional hybrid switch@MOF materials has become a central point of research in recent years . These smart composites are obtained by introducing photoswitchable dye molecules such as azobenzenes and (fluorinated) derivatives, diarylethenes or spiropyrans as non‐covalently attached guests into the crystalline porous MOF (metal‐organic framework) host scaffold.…”

Atomic/Molecular Layer Deposited Iron–Azobenzene Framework Thin Films for Stimuli‐Induced Gas Molecule Capture/Release

“…[9,10] Introduction of azobenzene moieties in porous MOF-like materials has already been challenged in recent studies. [17,18] Thef irst alternative would be truly exciting but difficult to realize;t he challenges arise from the fact that azobenzene is an integral part of ar igid crystal structure in which the trans-cis transformation either does not occur owing to the lack of free space,o ro ccurs but destroys the crystal lattice in an irreversible manner. [17,18] Thef irst alternative would be truly exciting but difficult to realize;t he challenges arise from the fact that azobenzene is an integral part of ar igid crystal structure in which the trans-cis transformation either does not occur owing to the lack of free space,o ro ccurs but destroys the crystal lattice in an irreversible manner.…”