Synthesis, structure and high methane storage of pure D6R Yb(Y) nonanuclear cluster-based zeolite-like metal-organic frameworks

Design and construction of highly porous and diverse zeolite-like metal-organic frameworks (ZMOFs) still remain a great challenge due to the limitation of current synthetic strategies. A double six-membered ring (D6R) is regarded as an effective but challenging secondary building unit to target ZMOFs. One most recent example of kex-MOF-1 is elegantly constructed from inorganic and organic D6Rs. Nevertheless, there is no documented structure built from pure inorganic D6Rs. Herein, solvothermal reactions between an angular dicarboxylate ligand and rare-earth (RE) ions in the presence of 2-fluorobenzoic acid afforded both 3-periodic RE-MOFs. Considering the newly formed nonanuclear RE clusters and ditopic linkers respectively behaving as pure inorganic D6Rs and connecting edges, both compounds display the well-known zeolitic topology of gme and result in two isostructural RE(Yb/Y)-ZMOFs. Thanks to the long distance of the ditopic ligand, both RE-ZMOFs possess considerably high surface areas and pore volumes, and subsequently demonstrate relatively high gravimetric methane storage working capacities.