Construction of ntt-Type Metal–Organic Framework from C2-Symmetry Hexacarboxylate Linker for Enhanced Methane Storage

Abstract

By using a shortened hexacarboxylate linker of C2-symmetry, a ntt-type metal–organic framework (UTSA-61) was constructed. Powder X-ray diffraction (XRD) crystallographic analysis revealed that UTSA-61 features the connection of the organic linker with four Cu2 paddlewheels and one large -[Cu2(O2CR)4-H2O-Cu2(O2CR)4]- cluster. This work confirms that a dendritic hexacarboxylate linker may support two cuboctahedral cages close to each other in ntt-type frameworks. Moreover, removing two ethynyl groups from PCN-61 (the prototypical ntt-type MOF) leads to optimized T-Td/T-Oh cages in UTSA-61 and results in preferable methane uptake than those of previously reported ntt-type MOFs. The activated UTSA-61a therefore exhibits a high methane storage capacity of 244 cm3 (STP) cm–3 at 298 K and 65 bar, and a high working capacity of 176 cm3 (STP) cm–3 (between 5 and 65 bar). These results rank UTSA-61a as one of the very few MOFs with both high volumetric methane storage and working capacities, rendering UTSA-61a as a...