Supramolecular interactions induced hinge-like motion of a metal–organic framework accompanied by anisotropic thermal expansion

Abstract

A novel three-dimensional metal–organic framework (MOF), Ag₄(tpt)₄{δ-[Mo₈O₂₆]}·1.5H₂O (A) (tpt = 2,4,6-tris(4-pyridyl)-1,3,5-triazine), possesses a ths-type topology with the hinge deformation mode. The single-crystal X-ray diffraction study shows that A and the dehydrated phase Ag₄(tpt)₄{δ-[Mo₈O₂₆]} (B) display distinct anisotropic thermal expansion with expansion in the b direction but contraction in the ac plane. This rare area negative thermal expansion (NTE) behavior is attributed to the hinged structure model and the supramolecular interactions (argentophilic interaction, π–π interaction) that act as the microscopic driving forces. In addition, supramolecular interactions also play a key role in thermochromic behavior of compound A.