Two-Dimensional Conductive Metal-Organic Framework for Small-Molecule Sensing in Aqueous Solution

Two-dimensional (2D) conductive metal-organic frameworks (cMOFs) have emerged as powerful transducers for electrochemical sensing. However, electrochemical sensing in aqueous solutions remains at a very early stage for 2D cMOFs. Herein, the interfacial capacitances of a 2D cMOF are utilized for electrochemical sensing for the first time. Various redox-innocent compounds along with redox-active compounds in aqueous solutions are successfully detected based on the responses of two capacitance peaks at low voltages. The quantitative sensitivity to ascorbic acid is even an order of magnitude higher than the previous voltammetric method. Further investigation demonstrates that the responses are rooted in the pseudocapacitances of the 2D cMOF, i.e., the transitions among the multiple redox states of the ligands. The analytes are suggested to alert the d-p conjugation and exchange electrons with the 2D cMOF. These deep insights in response mechanisms represent an important step for promoting the application of 2D cMOFs in chemical sensing.

Automated summary

Two-dimensional (2D) conductive metal-organic frameworks (cMOFs) have been used as transducers for electrochemical sensing, but its application in aqueous solutions is in the early stage. This study utilizes the interfacial capacitances of a 2D cMOF for the first time in electrochemical sensing. Various compounds, including redox-innocent and redox-active compounds, are successfully detected based on the responses of capacitance peaks at low voltages. The insights into the response mechanisms represent an important step in promoting the application of 2D cMOFs in chemical sensing.