Two new Ag-MOFs: Synthesis, structure, electrocatalytic hydrogen evolution and H2O2 electrochemical sensing

Two new Ag-MOFs with the chemical compositions of {[Ag4(Pobb)2(fum)2]·4H2O}n (1) and {[Ag4(Pobb)2(5-hip)2]·15·.5H2O}n (2) (Pobb = 1,3-bis(N-pyridyl-benzimidazol-4-yl)-2-oxopropane, fum = fumarate, 5-hip = 5‑hydroxy isophthalate) have been synthesized by volatilization method. Single crystal structural analysis showed that although both Ag-MOFs have a three-dimensional (3D) network backbone structure, the difference lies in the presence of Ag-Ag interactions in 2. The electrocatalytic hydrogen evolution reaction (HER) and H2O2 electrochemical sensing performance of Ag-MOFs 1–2 modified carbon paste electrodes 1-CPE and 2-CPE were investigated. Electrocatalytic HER investigations revealed the 1-CPE and 2-CPE exhibited highy efficient catalytic activity compared to the blank electrode in 0.5 M H2SO4 at current density of 10 mA cm−2 (η10) with their overpotential positively shifted by 277 and 307 mV, and Tafel slopes reduced by 345 and 373 mV dec-1, respectively. The 2-CPE exhibited superior electrocatalytic performance than 1-CPE probably attributed to the presence of Ag-Ag interactions in 2 and the mechanism of electrocatalytic HER was tentatively speculated. Electrochemical sensing studies indicated that 1-CPE and 2-CPE have the lower detection limits of 0.45 and 0.39 μM for H2O2 in the response range of 0.5 μM ∼ 4.0 mM and sensitivities of 4.73 and 22.65 μA mM−1. The splendid performance was probably attributed to the excellent electrocatalytic potential of Ag-MOFs.