A Novel Interpenetrated Cd(II)-Organic Framework and Its Composite with Hydroxyl-Functionalized Multi-Walled Carbon Nanotubes Showing Dual Electrochemical Sensing Behavior to 4-Nitrophenol and Acetaminophen

Abstract A novel 3D interpenetrated Cd(II)-organic framework with lonsdaleite topology, [Cd(asba)(bbtz)2(H2O)]·3H2O (Cd-AB), constructed from 2-amino-4-sulfobenzoic acid (H2asba) and a flexible linker, 1,4-bis(1H-1,2,4-triazol-1-ylmethyl)benzene (bbtz), was successfully synthesized via a facile slow evaporation method. Furthermore, its hybrid composite with hydroxyl-functionalized multi-walled carbon nanotubes (Cd-AB@HCNTs) was fabricated through a one-pot synthesis strategy. Amperometric measurements demonstrate that Cd-AB and Cd-AB@HCNTs modified glassy carbon electrodes (Cd-AB/GCE and Cd-AB@HCNTs/GCE) exhibit sensitive and selective electrochemical sensing towards 4-nitrophenol (4-NP) in 0.1 M H2SO4 and acetaminophen (APAP) in 0.1 M phosphate buffer solution (PBS, pH = 7.0), respectively. Remarkably, Cd-AB@HCNTs is capable of discriminating 4-NP from its isomers, 2-NP and 3-NP. Notably, the Cd-AB@HCNTs composite displays superior electrocatalytic activity for both the reduction of 4-NP and the oxidation of APAP compared to the pristine Cd-AB. The underlying sensing mechanisms for 4-NP and APAP were elucidated through Hirshfeld surface analysis and density of states (DOS) calculations. Moreover, this sensing platform was effectively extended to portable screen-printed electrode (SPE). Among the fabricated electrodes, the Cd-AB@HCNTs/SPE exhibited the most efficient sensing performance, with detection ranges of 0.2 μM to 2.20 mM for 4-NP and 0.5 μM to 2.75 mM for APAP. The corresponding limits of detection (LODs) were determined to be 37.8 nM for 4-NP (δ = 0.00796 μA, N = 10) and 71.4 nM for APAP (δ = 0.00258 μA, N = 10), respectively. Remarkably, the practical applicability of Cd-AB@HCNTs/SPE was validated by successfully detecting 4-NP and APAP in the actual samples, respectively.