DescriptionAt present, most developments based on microelectronics, sensing and optical devices rely on the technology of thin-film fabrication. Recently, numerous functional MOF thin films have been exploited and applied in these fields. Much interest has arisen in modulating of their physical properties, which may require selective engineering of the MOF porosity, or implementing susceptibilities to external stimuli, such as light to realize a photo-responsive system. One of the most straightforward strategies to alter the MOF structure by light is to infiltrate MOF pores with photo-responsive chromophores of suitable size (e.g., azobenzene). Herein, we study oriented thin films based on copper hydroxide nanobelts converted to Cu2bdc2,  serving as the supporting MOF for the subsequently grown flexible zinc-based DMOF-1 infiltrated by azobenzene. Our research aims to elucidate the photo-triggered structural dynamics in solid-state induced by the reversible photo-isomerization of azobenzene between its trans (ground state) and cis isomer. Hence, the isomerization of the infiltrated azobenzene inside the MOF pores forces the flexible framework structure to adapt to the trans/cis isomerization of the chromophore alternating between the ‘OFF’ and ‘ON’ state, respectively (Fig. 1, A). At the Austrian SAXS beamline located at the ELETTRA synchrotron radiation source, we have successfully switched the infiltrated thin films by UV light to the ‘ON’ state, whilst the recovery of the system was achieved by visible light irradiation (‘OFF’). The thereby provoked structural transitions of the crystalline film induced by the photo-switchable chromophore were investigated with time-resolved Grazing-Incidence Small Angle X-Ray Scattering (GISAXS). Thus, we demonstrate the very first reversible photo-response in oriented MOF films accompanied by structural changes of the solid-state host system on the timescale of seconds (Fig. 1, B). Further, pursuing our concept proposed herein allows us to reversibly switch the MOF system in centimetre-scale by remote-control, which makes the system highly attractive for the development of smart materials in e.g. optoelectronic applications. These results will allow us to gain further knowledge on the underlying structural transitions with the ultimate goal to understand and characterize the photo-induced dynamics in crystalline solids.
 Falcaro, P.; Okada, K.; et. al. Centimetre-scale micropore alignment in oriented polycrystalline metal-organic framework films via heteroepitaxial growth. Nature materials. 16, 342-348 (2017).
 Yanai, N.; Uemura, T. et. al. Guest-to-host transmission of structural changes for stimuli-responsive adsorption property. J. Am. Chem. Soc. 134 (10), 4501–4504 (2012).
|Period||1 Sep 2021 → 3 Sep 2021|
|Event title||S4SAS Conference 2021|
|Location||Virtual, OnlineShow on map|
|Degree of Recognition||International|
Fields of Expertise
- Advanced Materials Science