Metal-Cation-Independent Dynamics of Phenylene Ring in Microporous MOFs: A 2H Solid-State NMR Study

Abstract

Mobility of the organic linkers in metal–organic frameworks (MOFs) is an established phenomenon. Knowledge of the details of linker motion in MOFs could provide a great deal of information about the linker structure and the way the guest molecules interact with the organic framework. However, the mobility of the organic linkers is poorly characterized. The extent of the influence of the metal cation or guest molecules on linker motion is still unknown for MOFs with identical topologies. In this work, we have analyzed the rotational dynamics of the phenylene ring fragments of terephthalate (1,4-benzenedicarboxylate, bdc) linkers in the series of MOFs [M2(bdc)2(dabco)]·G (M = Co2+, Ni2+, Cu2+, Zn2+; dabco =1,4-diazabicyclo[2.2.2]octane; G = none or dimethylformamide, DMF). We have established that the reorientational motion of the phenylene rings is performed by π-flipping of the plane of the ring about its C2 axis. The dynamics of the phenylene rings is insensitive to the variation of the metal cation, whe...