A new multifunctional two-dimensional cobalt(II) metal–organic framework for electrochemical detection of hydrogen peroxide, luminescent sensing of metal ions, and photocatalysis

Abstract

A new multifunctional cobalt(II)-based metal–organic framework, [Co(DCTP)(L)(H2O)2]n (NCST-1, NCST = North China University of Science and Technology), was synthesized by self-assembly of Co(OAc)2·4H2O with 1,4-bis(benzimidazol-1-ylmethyl)-benzene (L) and 2,5-dichloroterephthalic acid (H2DCTP). Single-crystal X-ray diffraction analyses reveal that NCST-1 is a 2D (4,4) sheet, which is further expanded into a 3D supramolecular network by OH⋯O hydrogen bond interactions. A non-enzyme electro-catalytic sensor was developed for sensing hydrogen peroxide (H2O2) based on the NCST-1, which was cast-coated on glassy carbon electrode (GCE). The modified sensor exhibited a remarkable performance for H2O2 reduction with an extended liner range (5 μM–7 mM, 7 mM–18 mM), a fast response time (3 s), a high sensitivity (52.55 μA mM−1 cm−2), and a low detection limit (6.86 μM) in alkaline solution. Furthermore, NCST-1, as a luminescent probe, displayed prominent multifunctional sensing property for Fe3+, Hg2+ as well Ag+ through fluorescence quenching effect. The emission intensity of NCST-1 increases linearly with the increasing concentration of Fe3+ with a Stern–Volmer constant (Ksv) of 1.12 × 104 M−1 and a detection limit (LOD) of 0.13 μM in aqueous solution. For mercury ion (II), Ksv = 7.58 × 103 M−1 and LOD = 1.10 μM. For silver ion (I), Ksv = 6.22 × 103 M−1 and LOD = 1.33 μM. Finally, the photocatalytic activities of NCST-1 were evaluated in the degradation of methylene blue (MB), Rhodamine B (RhB), and methyl orange (MO). The degradation efficiency for MB reached up to 91.3%, although NCST-1 hardly showed degradation ability towards RhB and MO.