Complete Linker Desymmetrization Enabled Construction of an eft-Topological Zr(IV)-MOF Comprising Two Types of...

Rational design and serendipitous discovery constitute the two wheels of molecular science. Despite the fruitful achievements of constructing metal-organic frameworks from highly symmetric linkers under the guidance of reticular chemistry principles, the formulation of synthetic principles with unsymmetric organic linkers, while fundamentally important for targeting unexpected structures and functions, has been underdeveloped. Herein, we achieved a Zr(IV)-based MOF (SJTU-24) with a computationally modelled trinodal (3,4,8)-connected eft topology where two types of Zr₆ secondary building units (SBUs) co-exist, including an unprecedented 4-connected concave coordination figure, through a complete linker desymmetrization approach. This topology, to our knowledge, has not been experimentally achieved in Zr-based MOFs, highlighting the pivotal role of linker symmetry manipulation in the discovery of materials with non-default topology. SJTU-24 exhibits exceptional ammonia capture performance among Zr-based MOFs, reaching 14.1 and 4.8 mmol/g adsorption capacity at 1 and 0.1 bar, respectively. Semi-in situ Infrared (IR) and x-ray photoelectron spectroscopic (XPS) studies decipher that both the Brønsted acidic hydroxyl sites in the Zr₆ SBUs and the monodentately-coordinated carboxylate moieties in the linkers participate in the interactions with NH₃. This work, thus provides a valuable insight into leveraging complete linker desymmetrization engineering to unlock non-default and sophisticated structures with improved properties.