Control of Dynamic Motion in Coordination Frameworks for Energy-related Functions

Abstract

Crystalline coordination frameworks often have intrinsic molecular dynamics such as rotation, libration in wide temperature range. The cooperative motions in the frameworks are controllable by tuning of structural dimensionality, density, strength of coordination bond, etc. We focus on the motions of local structures in coordination frameworks, and apply them to construct solid state ion conductor and CO₂ separation material. In case of the synthesis of ion conductors, pinning of proton carriers such as imidazole and phosphate in coordination frameworks provides regular alignment for H⁺ hopping and it results high H⁺ conductivity under anhydrous condition. In case of CO₂ separation, the CO₂ molecule-responsive structural rearrangement of coordination framework is feasible by use of the local dynamics of coordination bonds. It enables specific molecular recognition of CO₂ and provides high CO₂ separation property over other gases (CH₄, C₂H₄, C₂H₆) without strong interaction. The gentle and selective capture of CO₂ via structural transformation does not require large energy consumption for CO₂ regeneration. In this review, we discuss the design and utilization of molecular motion in coordination framework solids for the energy-related functions.