A new Cd4-2,4-pyridinedicarboxylate layered coordination polymer consisting of intralayer cavities and reversible network self-adaptation upon dehydration/moisture-absorption

Abstract

A new robust, highly stable layered coordination polymer, [Cd₂(H₂O)₂(2,4-pyda)₂·H₂O]_n (FJU-3) (2,4-pyda = 2,4-pyridinedicarboxylate) consisting of hydrophilic box-shape intralayer cavities and terminally coordinated water molecules on the layer surfaces was assembled. Two new Cd-pyda coordination modes were observed, leading to the formation of a novel tetra-cadmium pyridinecarboxlate secondary building unit. The dehydration of FJU-3 results in empty hydrophilic cavities that modulate the metal coordination environments on the layer surfaces. The behaviour of dehydration/moisture-absorption of FJU-3 is reversible. Therefore, the regeneration of layer-to-layer hydrogen-bonding interactions results in the reversible transformation of the solid-state stacking of the layered supramolecular network, as evidenced by powder X-ray diffraction and thermogravimetric analyses. In the solid-state, FJU-3 exhibited high thermal stability.