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

Abstract

Three metal–organic frameworks {[Cu₆(L₁)₄(DMF)(H₂O)₂·5H₂O]}_n (1), {Cu₃(L₁)₂(phen)₂(H₂O)}_n (2) and {[Cu₈(μ₃-OH)₃(L₂)₄(NO₃)(H₂O)₅]·3H₂O}_n (3) utilizing nitrogen-containing heterocyclic carboxylate bifunctional ligands (L₁ = 5-(4-carboxypyridin-3-yl)isophthalic acid and L₂ = 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 μM and a limit of detection (LOD) of 0.097 μM. Therefore, the novel Cu-MOFs could be regarded as promising artificial enzyme mimics in catalysis, sensors and environment analysis.