A porous thiacalix[4]arene based metal-organic framework sensor combined with reduced graphene oxide and spherical graphite for highly sensitive electrochemical detection of caffeic acid

Caffeic acid (CA), featuring antibacterial and antiviral activity, is extensively present in plants. Excessive intake of CA poses a carcinogenic risk to human body. Thus, sensitive and convenient detection of CA is of great importance for human health. Herein, a porous Zn(II) cluster-based metal-organic framework (MOF), namely, [Zn10(BPDC)8L(mu 3-OH)4]center dot 19MeOH center dot 30H2O center dot 10DMA (Zn-L-BPDC), was successfully prepared (H2BPDC = 4,4 ' biphenyldicarboxylic acid, L = thiacalix[4]arene-based ligand, MeOH = methanol and DMA = N,Ndimethylacetamide). Subsequently, the sample of Zn-L-BPDC was well combined with highly conductive reduced graphene oxide (RGO) and spherical graphite (SG) to produce the three-component Zn-L-BPDC/RGO/SG composite. Under the optimal condition, Zn-L-BPDC/RGO/SG-2@GCE (GCE = glassy carbon electrode) exhibited a nanomolar level limit of detection (LOD, 0.96 nM) for CA. Markedly, this sensor was used to evaluate the content of CA in different food samples (cherry, blueberry, grape and tomato) with satisfactory recoveries (99.33-102.19 %). The ultraviolet-visible (UV-Vis) spectrophotometry and high-performance liquid chromatography (HPLC) technique were further conducted to validate the accuracy of this sensor for CA determination. This work developed a three-component MOF sensor combined with RGO and SG for quantitative analysis of CA in food samples.