Two difunctional Co(II) coordination polymers for natural sunlight photocatalysis of methylene blue and selective fluorescence sensing of Cr(VI) ion in water media

Abstract

Two new difunctional Co(II) coordination polymers (CPs), namely, [Co(TBTA)(L)1.5]n (1) and {[Co(NPHT)(L)]·H2O}n (2) were hydrothermally synthesized from 4,4′-bis(imidazole-1-yl)-biphenyl and different aromatic carboxylic acid ligands (H2TBTA = tetrabromoterephthalic acid, and H2NPHT = 3-nitrophthalic acid). Two CPs feature 2D (3,6)-connected hcb, and (4,4)-connected sql topologies for 1, and 2, respectively. 1 further extends into a three dimensional supramolecular architecture through π···π stacking interactions. Both of CPs exhibit high photocatalytic activities for degradation of methylene blue (MB) with remarkable efficiencies (85.83% for 1, and 93.76% for 2) under natural sunlight irradiation. 1 can sensitively and selectively detect Cr(VI) anions in water media with the Stern-Volmer quenching constant (Ksv) of 4.79 × 104 M−1 for Cr2O72− (pH = 3) or 2.36 × 104 M−1 for CrO42− (pH = 12). The linear detection ranges are 0–350 μM, and 0–200 μM for Cr2O72−, and for CrO42−, severally.