Dynamics and Proton Conduction of Heterogeneously Confined Imidazole in Porous Coordination Polymers

The nanoconfinement of proton carrier molecules may contribute to the lowing of their proton dissociation energy. However, the free proton transportation does not occur as easily as in liquid due to the restricted molecular motion from surface attraction. To resolve the puzzle, herein, imidazole is confined in the channels of porous coordination polymers with tunable geometries, and their electric/structural relaxations are quantified. Imidazole confined in a square-shape channels exhibits dynamics heterogeneity of core-shell-cylinder model. The core and shell layer possess faster and slower structural dynamics, respectively, when compared to the bulk imidazole. The dimensions and geometry of the nanochannels play an important role in both the shielding of the blocking effect from attractive surfaces and the frustration filling of the internal proton carrier molecules, ultimately contributing to the fast dynamics and enhanced proton conductivity.

Automated summary

The confinement of proton carrier molecules in nanostructures can reduce their proton dissociation energy. However, restricted molecular motion from surface attraction impedes the easy transportation of free protons. To address this issue, imidazole is confined in the channels of porous coordination polymers with tunable geometries, and its electric/structural relaxations are measured. Imidazole confined in square-shaped channels exhibits heterogeneity in dynamics with a core-shell-cylinder model. The dimensions and geometry of the nanochannels play a crucial role in shielding the blocking effect from attractive surfaces and facilitating the filling of internal proton carrier molecules, leading to enhanced dynamics and proton conductivity.