Photoswitching metal-organic frameworks: towards light controlled adsorptivity in porous materials

Abstract

Metal Organic Frameworks (MOFs) are porous material composed of metal nodes bridged by organic linkers. The resultant structures form porous 3-dimensional frameworks; the chemistry and applications of these materials is incredibly diverse. Through judicious choice of the metal coordination chemistry coupled with the imaginationlimited organic linker design, MOFs have been tailored for numerous applications including gas storage, gas separations, and catalysis. While these properties are easily tuned, they are considered static (i.e., the properties do not change once the MOF is formed). For this reason, research into the design of stimuli-responsive MOFs has gained notoriety in the MOF literature. This is owed to changeable adsorptivity in response to introduced stimuli such as heat, pressure, and light. This thesis discusses strategies to design PSZ-1, a new class of light-responsive MOFs that incorporates dithienylethene photoswitches into the pore lining. This new material behaves as a light controlled chemical filter and undergoes photoisomerization for a minimum of 5 times without degradation to the materials structure. Further work studied photophysical properties of a small family of structurally analogous DTEs, which are studied in order to understand the influence of 2-imidazoyl substituents on the thermal stability of these molecules. Finally, we report the synthesis of PSU-68, which has a controlled degrees of photoswitch incorporation and investigate the effect of linker loading on separation properties in the MOF.