Orthogonal Photoswitching in a Porous Organic Framework

The development of photoresponsive systems with non-invasive orthogonal control by distinct wavelengths of light is still in its infancy. In particular, the design of photochemically triggered-orthogonal systems integrated into solid materials that enable multiple dynamic control over their properties remains a longstanding challenge. Here, we report the orthogonal and reversible control of two types of photoswitches in an integrated solid porous framework, that is, visible-light responsive o-fluoroazobenzene and nitro-spiropyran motifs. The properties of the constructed material can be selectively controlled by different wavelengths of light thus generating four distinct states providing a basis for dynamic multifunctional materials. Solid-state NMR spectroscopy demonstrated the selective transformation of the azobenzene switch in the bulk, which in turn modulates N2 and CO2 adsorption. Two photoswitches, i.e., 6-nitro-spiropyran and o-fluoroazobenzene are shown to operate in a wavelength-orthogonal manner both in solution and when integrated into a porous material scaffold. Selective isomerization of each photoswitch can be triggered by a specific wavelength of light giving rise to four independently accessible states of the porous material, thus providing a basis for the dynamic multifunctional materials. image