Proton conduction and electrochemical glucose sensing property of a newly constructed Cu(II) coordination polymer

• A novel ionic Cu(II) coordination polymer 1 was constructed. • Hydrogen bonds exist extensively in 1 . • Indirect band gap exists in 1 . • The composite membrane of 1 with nafion shows interesting proton conduction properties. • 1 exhibits selective glucose oxidation sensing. The assembly between 5-sulfo-1, 2, 4-benzoic acid (H 4 SBTB) and Cu 2+ in the presence of 4, 4´-bipyridine (Bipy) results in a novel ionic coordination polymer with two crystallographically independent hexa-coordinated Cu1 and Cu2 ions, namely, [Cu 3 (HSBTB) 2 (Bipy) 3 (H 2 O) 8 ] n ( 1 ), which consists of an anionic Cu1 2 (C1O1O2) 2 -Bipy-bridged double-chain and a cationic Cu2-Bipy-bridged mono-chain. With the aid of H-bonds, the anionic Cu1 2 (C1O1O2) 2 -Bipy-bridged double-chains extend into a 2D supramolecular anionic double-layer, which is further linked by the cationic Cu2-Bipy-bridged mono-chain, resulting in a 3D supramolecular network. The H 4 SBTB acid exhibits a new coordination mode, i.e . one carboxyl group still remains protonated in 1 . The analysis of the solid-state diffuse reflectance UV-Vis-NIR spectrum reveals that the indirect bandgap exists in 1 , which was further illustrated by the theoretical calculation on the basis of Density Functional Theory (DFT) using the CASTEP program. The electrochemical studies indicate that the composite membrane of 1 with nafion shows interesting temperature-insensitive proton conduction behavior at pH = 3. Cyclic voltammograms indicate that 1 exhibits electrocatalysis to glucose oxidation in 0.1 M NaOH. The current-time (i-t) response curves reveal that 1 demonstrates sensitive and selective electrochemical oxidation sensing of glucose with an exponential detection range of 0-30 mM. The limit of detection (LOD) was calculated to be 38.74 μM. Temperature-insensitive proton conduction and electrochemical enzyme-free glucose sensing of an ionic Cu(II) coordination polymer 1 .