Unraveling the timescale of the structural photo response within oriented Metal Organic Framework films

Activity: Talk or presentationTalk at conference or symposiumScience to science

Description

Grazing incidence (wide-angle) X-ray scattering (GI(WA)XS) techniques that operate with short acquisition times, as provided by synchrotron sources, are a powerful tool to probe the structural evolution within soft-matter films when, e.g., applying a stimulus such as light irradiation [1]. Yet, photo-triggered structural changes in solid films are scarcely observed and if, the temporal response characteristics of the structure towards the incoming stimulus remain largely unknown [2]. In this work, for the first time, on the example of a preferentially oriented photo-responsive Metal-Organic Framework film system (DMOF-1/azobenzene) [3,4], the intrinsic timescales of the photo-triggered structural transformations within the crystalline film are studied and quantified [5,6]. When altering the length of the azobenzene molecule by photo-isomerization (trans-to-cis, 343 nm; cis-to-trans, 450 nm), we find that GIWAXS can decouple a flexible and non-flexible structural response within the oriented DMOF-1/azobenzene film system [4]. Hence, within 15 seconds, a reversible DMOF-1/azobenzene response along the (001) crystallographic axis occurs due to a cooperative movement of the DMOF-1 crystallites. The photo-response of our oriented DMOF-1/azobenzene film is one of the fastest observed structural transition for azobenzene-containing solid crystalline films, and one of the first for photo-responsive MOF films. Moreover, we demonstrate that the duration of the structural response can be deliberately tuned by altering the aspect ratio of the DMOF-1 crystallites [4]. Our work thereby suggests a new avenue to elucidate the timescales and the photo-responsive behaviour in similar or even more advanced soft-matter film systems.
Period16 Sep 2022
Event title18. International Small-Angle Scattering Conference: SAS 2022
Event typeConference
LocationCampinas, BrazilShow on map
Degree of RecognitionInternational

Fields of Expertise

  • Advanced Materials Science