The first porous MOF with photoswitchable linker molecules

We synthesized a porous twofold interpenetrated MOF [Zn 2 (NDC) 2 (1)] (coined CAU-5) using 3-azo-phenyl-4,4¢-bipyridine (1), 2,6-naphthalenedicarboxylic acid, and Zn(NO 3 ) 2 · 6H 2 O. The azo-functionality protrudes into the pores, and can be switched, by irradiation with UV light (365 nm), from the thermodynamically stable trans-isomer to the cis-isomer. Back-switching was achieved thermally and with an irradiation wavelength of l max = 440 nm