A series of novel Cu-based MOFs: syntheses, structural diversity, catalytic properties and mimic peroxidase activity for colorimetric detection of H2O2

Three metal-organic frameworks {[Cu-6(L-1)(4)(DMF)(H2O)(2)center dot 5H(2)O]}(n) (1), {Cu-3(L-1)(2)(phen)(2)(H2O)}(n), (2) and {[Cu-8(mu(3)-OH)(3)(L-2)(4)(NO3)(H2O)(5)]center dot 3H(2)O}(n) (3) utilizing nitrogen-containing heterocyclic carboxylate bifunctional ligands (L-1 = 5-(4-carboxypyridin-3-yl)isophthalic acid and L-2 = 2-(5-carboxypyridin-2-yl)terephthalic acid) were self-assembled hydrothermally and characterized. MOFs 1-3 possess 3D networks which consist of three different types of Cu clusters {Cu2O2(OCO)(4)}, {Cu2O2N4(OCO)(2)} and {Cu4O10(OCO)(4)}, respectively. MOFs 1-3 efficiently catalyze the oxidation of cycloalkanes under mild conditions. Besides, the synthesized MOFs 1-3 exhibited high peroxidase-like activity and could be utilized to catalyze the oxidation of 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid ammonium salt) (ABTS) to produce green color in the presence of hydrogen peroxide (H2O2). The steady-state kinetics experiments of the oxidation of ABTS catalyzed by MOFs 1-3 were carried out, and the kinetic parameters were obtained. The results indicated that the affinity of MOFs 1-3 towards H2O2 and ABTS was higher than that of the natural horseradish peroxidase (HRP). The as-prepared MOF 1 can be applied for the colorimetric detection of H2O2 with a wide linear range of 0.5 to 200 mu M and a limit of detection (LOD) of 0.097 mu M. Therefore, the novel Cu-MOFs could be regarded as promising artificial enzyme mimics in catalysis, sensors and environment analysis.