Tetrazole-Functionalized Zirconium Metal-Organic Cages for Efficient C2 H2 /C2 H4 and C2 H2 /CO2 Separations.

Isoreticular functionalization is a well-elucidated strategy for pore environment tuning and the basis of gas separation performance in extended frameworks. The extension of this approach to discrete porous molecules such as metal-organic cages (MOCs) is conceptually straightforward but hindered by synthetic complications, especially stability concerns. We report the successful isoreticular functionalization of a zirconium MOC with tetrazole moiety by bottom-up synthesis. The title compound (ZrT-1-tetrazol) shows promising C2 H2 /CO2 and C2 H2 /C2 H4 separation performance, as demonstrated by adsorption isotherms, breakthrough experiments, and density functional theory calculations. The design analogy between MOFs and highly stable MOCs may guide the synthesis of novel porous materials for challenging separation applications.