Finding the Optimal Balance between the Pore Size and Pore Chemistry in Hybrid Ultramicroporous Materials for Trace Acetylene Capture

The development of porous coordination networks based on square grids pillared by inorganic anions has attracted attention thanks to their benchmark gas sorption properties (e.g., high uptake capacity at low partial pressures; high selectivity). These properties are imparted by combining ultramicropores with strong electrostatics. Such hybrid ultramicroporous materials (HUMs) are also modular in nature and therefore amenable to systematic design via crystal engineering. Herein, we report the trace acetylene-capture-from-ethylene performance of two new interpenetrated HUMs with primitive cubic (pcu) topology, TIFSIX-14-Cu-i and NbOFFIVE-2-Cu-i. The sorption performances of these two materials were compared with those of three existing isostructural HUMs including the current benchmark, SIFSIX-14-Cu-i. Our results reveal that, whereas all five materials exhibit an excellent separation performance, small increases in the pore size from larger anions such as TIFSIX and NbOFFIVE more than counteracts their stronger electrostatics. SIFSIX-14-Cu-i, therefore, remains the benchmark material despite its weaker electrostatics.