Photoswitchable Conductive Metal–Organic Frameworks

Advanced materials with physical properties such as electric conductivity that can be dynamically controlled by remote signals will enable new cutting-edge applications. To date, while many materials with either photoswitchable conduction properties or high conductivities have been presented, the combination of both properties remains a challenge. Here, a series of conductive metal–organic framework (MOF) thin films is presented where the conductivity is reversibly remote controlled by light. The structures of the MOFs are Cu3(2,3,6,7,10,11-hexahydroxytriphenylene)2 (Cu3(HHTP)2) with different photochromic molecules of type azobenzene (AB), diarylethene (DAE), spiropyran (SP) and hexaarylbiimidazole (HABI) derivatives embedded in the MOF pores. By photoisomerizations of the guest molecules, induced by UV light and reversed by visible light irradiation or thermal relaxation, the conduction properties of the photoswitch@Cu3(HHTP)2 films are reversibly modulated by up to 15%. These changes of the electrical conductivity can be understood by calculating the density of states (DOS) near the Fermi level, showing that the DOS decreases upon embedment of the guest molecules and as a result of their isomerization. ... mehrMoreover, the application of such photoswitch@Cu3(HHTP)2 films as photoprogrammable gas sensors is demonstrated. With the introduction of photoswitchable conductive hybrid material, this study contributes to the extension of smart materials for innovative applications.