Ni-based metal-organic framework sensor material for urea detection: Mechanistic insights and performance
Maria Rita Ortega-Vega, Yutong Luo, Matthias Werheid, Inez M. Weidinger, Irena Senkovska, Julia Grothe, Stefan Kaskel
Abstract
A mechanistic study of the metal-organic framework nickel-hexahydroxytriphenylene [Ni 3 (HHTP) 2 ] n as an active catalyst material for electrochemical urea sensing is reported, together with the evaluation of its performance. Urea sensing is a crucial technology for the life quality of people facing kidney disease. Through the quantification of urea in saliva, the monitoring of the progress of kidney disease could be enabled. [Ni 3 (HHTP) 2 ] n can detect urea via urea electro-oxidation reaction. The urea electro-oxidation on [Ni 3 (HHTP) 2 ] n follows an EC’ mechanism. [Ni 3 (HHTP) 2 ] n is electrochemically transformed into Ni(OH) 2 , the catalytic intermediate of Ni in alkaline electrolyte, and the reduction step of Ni 3+ to Ni 2+ limited by the urea electro-oxidation reaction. The transformation leads to a disintegration of the metal-organic framework due to oxygen evolution. As urea inhibits oxygen evolution, the degradation is also inhibited. Our results demonstrated a competitive sensor when compared to the benchmarking, with a sensitivity of 1.797 mA/cm 2 ∙mM Urea, the limit of detection of 3.5 µM, linear range between 0.01 mM and 1 mM with a correlation coefficient of 0.991 and selectivity towards Na + , K + , Cl − , creatinine, uric acid , and low concentrations of glucose.