Construction of pyridine-functionalized metal–organic frameworks for the detection of flazasulfuron

Two novel Cu-based metal–organic frameworks (MOFs), namely, poly[[aquadichlorido[μ 4 -4′-(pyridin-4-yl)-[2,2′:6′,2′′-terpyridine]-4,4′′-dicarboxylato][μ 3 -4′-(pyridin-4-yl)-[2,2′:6′,2′′-terpyridine]-4,4′′-dicarboxylato]tricopper(II)] monohydrate], {[Cu 3 (C 22 H 12 N 4 O 4 ) 2 Cl 2 (H 2 O)]·H 2 O} n or {[Cu 3 (PTP) 2 Cl 2 (H 2 O)]·H 2 O} n , ( I ), and poly[[diaquabis[μ 2 -4′-(pyridin-3-yl)-[2,2′:6′,2′′-terpyridine]-4,4′′-dicarboxylato]bis(μ 2 -terephthalato)tricopper(II)] dihydrate], {[Cu 3 (C 22 H 12 N 4 O 4 ) 2 (C 8 H 4 O 4 ) 2 (H 2 O) 2 ]·2H 2 O} n or {[Cu 3 (BDC) 2 (MTP) 2 (H 2 O) 2 ]·2H 2 O} n , ( II ), have been synthesized successfully with 4′-(pyridin-4-yl)-[2,2′:6′,2′′-terpyridine]-4,4′′-dicarboxylic acid (H 2 PTP) and 4′-(pyridin-3-yl)-[2,2′:6′,2′′-terpyridine]-4,4′′-dicarboxylic acid (H 2 MTP) as the ligands, respectively. Crystal structure analysis reveals that ( II ) possesses a 2D coordinated layer structure, in which adjacent 2D coordination layers are linked into 3D frameworks through π–π interactions, while the structure of ( I ) displays dual coordination layers, in which adjacent coordination layers are connected into a 3D framework through hydrogen-bonding interactions. The photophysical properties of the two MOFs were investigated by fluorescence spectroscopy. Complex ( II ) shows an obvious `turn-on' fluorescence enhancement effect towards flazasulfuron and its potential application for sensing flazasulfuron in water with high selectivity and sensitivity was also investigated in detail.