Modulation of the Photophysics and Internal Dynamics in a Zr Metal Organic Framework by the Inclusion of Fluorinated Guests

Abstract

Herein, we report the precise modulation of the fast rotational dynamics in the MOF UiO-68 by the adsorption of 1,4tetrafluorobenzoquinone (TFBQ) or hexafluorobenzene (F 6 Bz). In the case of TFBQ, the infiltration was accompanied by the simultaneous generation of CT complexes inside the material's pores. As evidenced by deuterium solid-state NMR and computational simulations, the strong π−π stacking between the central phenylene rings of the organic linkers with the fluorinated molecules significantly reduced the rotational frequency (from hundreds to a few of MHz at room temperature) according to guest concentration. Furthermore, the CT interaction between TFBQ and the molecular rotors changed the photophysical properties of the crystalline MOF, as confirmed by electron-spin resonance, UV− vis, and PL measurements. This work constitutes a step forward in the development of stimuli-responsive advanced materials that exhibit a change in the internal mobility as well as the modulation of their photophysics.