Proton conduction and electrochemical enzyme-free glucose sensitive sensing based on a newly constructed Co-MOF and its composite with hydroxyl carbon nanotubes

Abstract

It is a great challenge to construct MOFs-based materials with low activation energy for potential applications in proton exchange membrane fuel cells (PEMFCs) as well as fine electrocatalytic glucose sensing performance. Herein, we report a novel 2D Co-MOF {[Co(iip)(bbbm)(H2O)2]·2DMF·2H2O}n obtained through the assembly between Co(II) and 5-iodoisophthalic acid (H2iip) in the presence of the hydrophobic ligand 1,1-(1,4-butanediyl)bis-1H-benzimidazole (bbbm). Its composite with hydroxyl-functionalized carbon nanotubes (Co-MOF@CNTs) was fabricated under ambient conditions. The (8) hydrogen-bonded ring exists in Co-MOF. Both the composite membranes of Co-MOF and Co-MOF@CNTs with nafion exhibit interesting proton-conductive behavior, which are even superior to that of nafion in aqueous medium with the same pH values. Among them, the proton conductivity of the composite Co-MOF@CNTs/nafion membrane is expectedly superior to that of the composite Co-MOF/nafion membrane. Remarkably, the composite Co-MOF@CNTs/nafion membrane exhibited an exceptionally low activation energy (Ea = 0.082 eV, pH = 3), which is among one of the lowest Ea values for the reported novel proton-conducting polymeric materials/composites, resulting in almost unchanged conductivity over the measured temperature range, revealing its potential application in PEMFCs. Moreover, both the pristine Co-MOF and its composite Co-MOF@CNTs could serve as electrocatalytic materials toward glucose oxidation. The Co-MOF@CNTs electrode exhibits expectedly more rapid and sensitive electrochemical glucose sensing with relatively lower determination limit (LOD = 3 μM) and larger detection range (0.01–5 mM) in comparison with that of the pristine Co-MOF (LOD = 0.021 mM, 0.01–2.40 mM).