A pyrazole-functional 3D cobalt-organic framework for fluorescence detection of Cu2+ and Hg2

•>A 3D cobalt(II) MOF with reserved pyrazole N sites was successfully synthesized.•> Compound 1 detects Cu2+ and Hg2+ by fluorescence quenching, and the quenching efficiency nearly up to 100%.•> Compound 1 has low detection LOD for Cu2+.•> The quenching mechanisms were investigated in detail. A new MOFs luminescent probe with the formula of [Co3(L)2(H2O)6]n (1) was synthesized via a solvothermal reaction with a triangular ligand 1,3,5-(tris(1-(4-carboxyphenyl)-1H-pyrazol-3-yl))benzene (H3L) and Co nitrate. Single-crystal X-ray diffraction analysis revealed compound 1 features a 3D network, which was constructed by 1D Co-O chains and μ5-connected L3− ligands. It is noteworthy that pyrazole N atoms of the ligand were uncoordinated in the framework. Detailed luminescent investigations reveal that compound 1 could sever as a highly selective and sensitive “turn off” luminescent probe toward Cu2+ or Hg2+ in DMA solution. The possible luminescent quenching mechanism of compound 1 by Cu2+ or Hg2+ can be attributed to the weak Lewis acid-base interaction between Cu2+ or Hg2+ and pyrazole N atoms. A 3D cobalt-organic framework containing uncoordinated pyrazole units as reserved host-guest binding sites were successfully constructed, which conduct luminescent detection Cu2+ and Hg2+ sensitively and selectively through strong fluorescence quenching process. The detection mechanisms have been proposed through PXRD and XPS in detail. [Display omitted]