Preparation and Analyses of the Multifunctional Properties of 2D and 3D MOFs Constructed from Copper(I) Halides and Hexamethylenetetramine

In this article, two two-dimensional and three-dimensional metal-organic frameworks are synthesized by the self-assembly of copper(I) halide and the hexamethylenetetramine (hmt) ligand. Compound 1 is a two-dimensional metal-organic framework composed of a pyramidal Cu4I5 cluster and hexamethylenetetramine, in which hmt-bridged Cu clusters form a two-dimensional (4,4)-connected net with a point symbol of (4(4).6(2)) (4(4).62). Compound 2 is a homochiral three-dimensional metal-organic framework material generated through an unusual spontaneous crystallization from achiral precursors. The two compounds were characterized by a series of analyses such as infrared spectroscopy, elemental analysis, circular dichroism spectroscopy, and powder X-ray diffraction. Both of them exhibit unexpected stability under a wide range of conditions of acid and base. In addition, the fluorescence intensity changes regularly under acid-base conditions. Stokes shift shows a good linear relationship with -log [H+], which makes them become promising acid-base sensors. Compounds 1 and 2 also display selective adsorption and a significant degradation effect on the organic dye methylene blue. In addition, the fluorescence study indicated that compound 2 could be used as a sensor to detect Cr3+.