Utilising Metal Melts of Low‐Melting Metals as a Novel Approach for MOF Synthesis: The 3D‐Imidazolate 3∞[Ga2(Im)6ImH] from Gallium and Imidazole

Abstract

AbstractMetals with low melting points like gallium (mp. 30 °C) prove a new approach for the synthesis of MOFs. As the melting point of gallium is even lower than of the linker ligand imidazole, formation of the MOF ${}^3_\infty[\textrm{Ga}_2(\textrm{Im})_6\textrm{ImH}]$, Im– = imidazolate anion, ImH = imidazole, can be achieved by reaction of a melt of the referring metal with a melt of the ligand. Gallium is oxidised in the reaction, and hydrogen gas and the imidazolate amide as colourless single crystalline product are formed. At the melting point of imidazole (mp. 88–90 °C) two liquid phases are observed. Phase separation lasts until the reaction, starting at 120 °C, consumes the liquid reagents. We consider this a reaction on the phase border between the liquid phases as no mixing is observed. ${}^3_\infty[\textrm{Ga}_2(\textrm{Im})_6\textrm{ImH}]$ constitutes of a three‐dimensional framework structure with a 3,6 topology that is built of two Kagome nets sharing common connectivity points. Each Ga3+ ion is octahedrally coordinated by six nitrogen atoms of imidazolate and imidazole ligands. The framework exhibits a limited porosity of 8.5 % of accessible space and a diameter of 376–509 pm for the pore windows.