Electrochemistry sensing of ascorbic acid based on conductive metal-organic framework (Cu₃(benzenehexathiol))...

Bulk-type conductive metal-organic frameworks (c-MOFs) had been applied to modify the electrode and used in electrochemical sensing because of the high conductive properties. But which still suffer from low mass permeability, restricted active site exposure, and poor accessibility due to the coordination saturation at metal sites in the bulk-type c-MOF. Recent studies have demonstrated that transforming bulk-type MOFs into MOFs nanosheets (NSs) can maximize the exposure of active sites and mass transfer. However, c-MOF NSs have rarely been applied in electrochemical sensing.

This study presents NSs type c-MOF Cu₃(benzenehexathiol) (CuBHT), synthesized using a simple sacrificial template method. CuBHT NSs were modified onto a glassy carbon electrode (GCE) to prepare CuBHT NSs/GCE, which was then applied to sense the model target ascorbic acid (AA), the system exhibits high sensitivity of 1.521 mA mM^-1 cm^-2 and a wide linear range of 1-789 μM, low detection limit of 0.46 μM. The sensitivity is 1.90 times higher than that of bulk-type CuBHT nanoparticles (NPs) modified GCE, which can be attributed to the CuBHT NSs having more exposed Cu sites on their surfaces. CuBHT NSs/GCE was then used to monitor AA levels in human sweat during daily activities or exercise, and the results indicated high reliability compared to the vitamin C ASA kit method.

The design of c-MOF CuBHT NSs/GCE lead to better performance in terms of sensitivity and low detection limit in AA sensing compared to bulk-type nanoparticles. The AA sensing mechanism based on CuBHT was investigated, and the sensing system was demonstrated by detecting AA in sweat. This work advances both the fundamental understanding and practical applications of c-MOF NSs in AA sensing.