Luminescent metal-organic frameworks (MOFs) as a chemopalette: tuning the thermochromic behavior of dual-emissive phosphorescence by adjusting the supramolecular microenvironments.

Two classical copper(I)-cluster-based luminophores, namely, Cu4I4 and [Cu3Pz3]2 (Pz = pyrazolate), are immobilized in a supramolecular system through the formation of metal-organic framework (MOF) materials. This series of luminescent MOF materials, namely, [Cu4I4(NH3)Cu3(L1)3]n, [Cu4I4(NH2CH3)Cu3(L1)3]n, and [Cu4I4Cu3(L2)3]n (L1 = 3-(4-pyridyl)-5-(p-tolyl)pyrazolate; L2 = 3-(4-pyridyl)-5-(2,4-dimethylphenyl)pyrazolate), exhibit diverse thermochromism attributed to the relative functioning efficacy of the two coordination luminophores. Such an intriguing chemopalette effect is regulated by the different supramolecular microenvironments between the two-dimensional layers of these MOFs, and in particular, by the fine-tuned Cu-Cu distances in the excimeric [Cu3Pz3]2 luminophore. The structure-property elucidation of the thermochromic behavior allows one to understand these optical materials with unusual dual-emissive properties.