A metal–organic framework gel with Cd2+ derived from only coordination bonds without intermolecular interactions and its catalytic ability

Abstract

A cyclohexane-based ligand (1) as a triconnected linker forms a supramolecular gel in the presence of transition metal ions, particularly Cd²⁺ and Zn²⁺. 1 can also be gelated with cadmium counter ions such as NO₃⁻, ClO₄⁻ and SO₄²⁻. The gels have been characterized by SEM, TEM, rheometry and single crystal X-ray crystallography. The Cd²⁺–cyclohexane-based ligand gel shows a fibrillar structure with diameters ranging from 20–50 nm. X-ray analysis revealed that 1 forms a 1D coordination polymer structure with the Cd²⁺ ion, with an octahedral structure. The rheological properties of the Cd²⁺–cyclohexane-based ligand gel were strongly dependent on the concentration of Cd²⁺. Furthermore, the xerogel 1 with Cd²⁺ acted as a base catalyst in the Knoevenagel condensation reaction.