Tetrazine-Based Metal-Organic Frameworks as Scaffolds for Post-Synthetic Modification by the Click Reaction

Metal-organic frameworks are one of the most active research fields today. Despite the progress in recent years, synthesis of highly porous structures bearing functional groups for specific applications remains a challenge. Here, we describe synthesis of Zr(IV) and Hf(IV)-based tetrazine containing metal-organic frameworks, ZrTz-68 and HfTz-68 with pore size of 2.1 nm, specific surface area up to 4217 m² g^–1, and a UiO-68 topology. The synthesis can be done on a multi-gram scale from inexpensive linker 4,4'-(1,2,4,5-tetrazine-3,6-diyl)dibenzoic acid (H₂TzDB). Moreover, because of the π-conjugated tetrazine groups these MOFs can be easily post-synthetically modified by a “click” reaction maintaining the crystallinity of the framework. Due to the diversity of “clickable” substituents, this strategy represents highly versatile tool for a wide range of applications.