Fluorescent Aromatic Tag-Functionalized MOFs for Highly Selective Sensing of Metal Ions and Small Organic Molecules

By varying the fluorescent tags of resorcin[4]­arene-based tetracarboxylic acids from phenyl to naphthyl, two highly luminescent metal–organic frameworks (MOFs), namely, [Zn₂(TPC4A)­(DMF)­(H₂O)₄]·3H₂O (1) and [(CH₃)₂NH₂]₂­[Zn­(TNC4A)]·4H₂O (2), were successfully achieved (TPC4A = 2,8,14,20-tetra-phenyl-6,12,18,24-tetra-methoxy-4,10,16,22-tetra-carboxy-methoxy-resorcin[4]­arene and TNC4A = 2,8,14,20-tetra-1-naphthal-6,12,18,24-tetra- methoxy-4,10,16,22-tetra-carboxy-methoxy-resorcin[4]­arene). Compound 1 features a unique 2D network, while 2 exhibits a fascinating 3D framework. The highly selective detection of small organic molecules as well as Fe²⁺ and Fe³⁺ was performed for 1 and 2 as fluorescent sensors. Remarkably, luminescent 1 and 2 were used as sensory materials for the sensing of various amine vapors with high selectivity and rapid response. Most strikingly, clear fluorescence “on–off” switch-functions toward small organic molecules as well as amine vapors were also explored for luminescent 1 and 2.