Reticular Chemistry in Its Chiral Form: Axially Chiral Zr(IV)-Spiro Metal-Organic Framework as a Case Study

The interplay of primary organic ligands and inorganicsecondarybuilding units (SBUs) has led to a continual boom of reticular chemistry,particularly metal-organic frameworks (MOFs). Subtle variationsof organic ligands can have a significant impact on the ultimate structuraltopology and consequently, the material's function. However,the role of ligand chirality in reticular chemistry has rarely beenexplored. In this work, we report the organic ligand chirality-controlledsynthesis of two zirconium-based MOFs (Spiro-1 and Spiro-3) with distincttopological structures as well as a temperature-controlled formationof a kinetically stable phase (Spiro-4) based on the carboxylate-functionalizedinherently axially chiral 1,1 '-spirobiindane-7,7 '-phosphoricacid ligand. Specifically, Spiro-1 is a homochiral framework comprisingonly enantiopure S-spiro ligands and has a unique4,8-connected sjt topology with large 3D interconnectedcavities, while Spiro-3 contains equal amounts of S- and R-spiro ligands, resulting in a racemic frameworkof 6,12-connected edge-transitive alb topology with narrowchannels. Interestingly, the kinetic product Spiro-4 obtained withracemic spiro ligands is built of both hexa- and nona-nuclear zirconiumclusters acting as 9- and 6-connected nodes, respectively, givingrise to a newly discovered azs net. Notably, the preinstalledhighly hydrophilic phosphoric acid groups combined with large cavity,high porosity, and outstanding chemical stability endow Spiro-1 withremarkable water vapor sorption performance, whereas Spiro-3 and Spiro-4show poor performances due to inappropriate pore systems and structuralfragility upon the water adsorption/desorption process. This workhighlights the important role of ligand chirality in manipulatingthe framework topology and function and would further enrich the developmentof reticular chemistry.

Automated summary

The interplay of primary organic ligands and inorganic secondary building units has led to the development of metal-organic frameworks (MOFs) in reticular chemistry. This study explores the role of ligand chirality in controlling the synthesis of different MOFs. The findings show that ligand chirality impacts both the structure and function of the MOFs, highlighting its importance in reticular chemistry.