A multifunctional Cd(ii)-based metal–organic framework with amide groups exhibiting luminescence sensing towards multiple substances

Abstract

A solvothermal reaction of an amide-functionalized tetracarboxylate linker (H₄L) with Cd(II) leads to an anionic metal–organic framework, (Me₂NH₂)₂[Cd₃(L)₂]·7H₂O (1). Incorporating the flexible amide group into the skeleton of H₄L causes the entire molecule to be twisted. Consequently, H₄L can behave as a tetrahedral node and further combine with cubic trinuclear [Cd₃(COO)₈] nodes to afford a rare (4,8)-connected fluorite (flu) net. More importantly, 1 contains an anionic framework featuring a channel decorated with amide groups, and thus exhibits a multi-responsive behavior towards Fe³⁺, Cu²⁺ and Cr₂O₇²⁻ ions in water as well as nitroaromatics in acetonitrile based on the turn-off effect. The possible quenching mechanism inferred that the amide groups decorated in the framework facilitate effective interactions through the formation of hydrogen bonds with analytes causing a change in luminescence signals.