Cationic metal organic frameworks synthesized from cyclotetraphosphazene linkers with flexible tentacles

MOFs based on group 12 metals, namely, [Zn2(O3PyCP)Cl4] (Zn-O3PyCp), [Cd(O3PyCP)(NO3)2].H2O (Cd-O3PyCp), and [Hg(O3PyCP)Cl2] (Hg-O3PyCp), were synthesized using a novel flexible molecular building block, octakis(3-pyridyloxy)cyclotetraphosphazene (O3PyCP), and group 12 metal salts (ZnCl2, Cd(NO3)2.6H2O, HgCl2). The crystals of each of the cationic frameworks were structurally characterized by single crystal X-ray diffraction, elemental, FT-IR, and thermogravimetrical (TGA) analysis. Due to the flexibility of O3PyCP building block, we were able to observe three distinct cationic frameworks with group 12 metal ions. We performed the atomically detailed simulations to compute H2 adsorption isotherms of the resulting frameworks at a pressure range of 0–1 bar at 77 K. Zn-O3PyCp exhibits the highest H2 uptake capacity (58.42 cm3 STP/g).