A Flexible Zn-MOF: Gate-Opening Adsorption Behavior and Selective Fluorescence Detection of Ethylenediamine

High Resolution Image Download MS PowerPoint Slide A new flexible Zn(II)-based metal–organic framework, namely, [Zn 2 (2,6-ndc) 2 (pvq)]·4.5DMF·0.5H 2 O ( Zn-MOF-α ), was solvothermally synthesized using 2,6-naphthalenedicarboxylate acid (2,6-H 2 ndc) and 5-(2-(pyridin-4-yl)vinyl)quinoline (pvq) as coligands. Single-crystal X-ray diffraction analyses revealed that Zn-MOF-α features a 2-fold interpenetrated framework with a primitive cubic ( pcu ) topology. Upon activation, Zn-MOF-α with 3D porous channels transformed into Zn-MOF-β (0D voids), involving significant changes in the metal–carboxylate coordination geometry, rotation of organic linkers, and relative sliding of the interpenetrated nets. Gas adsorption tests indicated that Zn-MOF-β displays no affinity for N 2 at 77 K but demonstrates a two-step CO 2 adsorption at 195 K. Additionally, Zn-MOF-β shows a significantly higher adsorption capacity for benzene (Bz) compared to cyclohexane (Cy) at 298 K. Fluorescence sensing experiments demonstrated that Zn-MOF-α exhibits significant fluorescence quenching in the presence of ethylenediamine. Remarkably, the Stern–Volmer quenching constant ( K sv ) for ethylenediamine reached 7.6 × 10 3 M –1, with a detection limit of 5.78 × 10 –6 M and a rapid quenching response time (<15 s). The underlying quenching mechanism was investigated and elucidated through systematic experiments. Furthermore, ethylenediamine detection was visually realized using a smartphone platform, enabling rapid and practical detection.