[Zn(C₃H₃N₂)(C₃H₂N₂–N=N–C₆H₅)], a Mixed‐Linker ZIF Containing a Photoswitchable Phenylazo Group

Abstract

Abstract We report the synthesis and characterization of the new switchable Zn‐based zeolitic imidazolate framework (ZIF) [Zn(Im)(aIm)] ( 1 ). The high‐throughput investigation of the mixed linker system Zn 2+ /imidazole (HIm)/2‐phenylazoimidazole (HaIm)/DMF at 85 °C led to 1 , which is isostructural to ZIF‐8 and crystallizes in a sodalite (SOD)‐type structure. The preparation was also studied with microwave‐assisted heating and ultrasound‐assisted synthesis. The crystal structure was determined from single‐crystal X‐ray diffraction data. Although Im – and aIm – ions are present in a 1:1 molar ratio, no ordering of the 2‐phenylazo group was observed. Incorporation of the Im – and aIm – linkers as an integral part of the framework structure was confirmed by elemental analysis, 13 C and 15 N MAS NMR, IR and Raman spectroscopy. In addition, the permanent porosity of 1 was demonstrated by N 2 sorption experiments and a specific surface area of S BET = 580 m 2 g –1 is observed. The photoswitching properties were investigated by UV/Vis spectroscopy as the cis and trans isomers exhibit different UV absorption spectra. Switching can be achieved by irradiation with UV light ( λ = 355 nm), and back‐switching using visible light ( λ = 525 nm). Although changes in the UV/Vis spectra are detected, the switching process is only partially reversible.