Thiazole and Pyrazole-based Metal-Organic Frameworks for Gas Storage and Catalysis

Metal-Organic Frameworks (MOFs) are coordination networks containing potential voids formed by metal ions or oxo-metallic clusters connected by polytopic ligands, with over 80,000 crystal structures reported so far. The extraordinary versatility in MOFs design (achieved through the tailored combination of linkers and metallic nodes) is the main reason of the applicative success of this class of materials. MOFs have unique advantages including the control of pore shape and dimensionality, tailored chemical environment and large surface area. The presence of heterocycles in the MOF organic linker opens new perspectives for a number of practical applications, like gas storage and catalysis. Among the various options, pyrazoles and thiazoles are intriguing, for different reasons. The former give rise to exceptionally stable (bridging) coordinative bonds with transition metals, imparting high thermal and chemical stability to the final material; the latter are the simplest (N,S) heterocycles conceivable and exhibit fluorescence properties (benzothiazoles are present in luciferines, bioluminescent substances that are produced by fireflies). MOFs featuring pyrazole- and thiazole-based linkers as organic building blocks (Figure 1) have been prepared and fully characterized in the solid state. Their performance as CO2 storage materials [1] and as heterogeneous catalysts for carbon dioxide conversion into cyclic carbonates under green conditions [2] has been scrutinized. The results will be presented.