Water-Mediated Proton Conduction in Metal–Organic Frameworks with High Water Stability Constructed by a Terpyridine Tricarboxylate Ligand

In this work, we design and synthesize one organic molecule solid-state material and three metal-organic frameworks, (H3tcpbmiddotH2O)n (H3tcpb-H2O), [Mn2(Htcpb)-(mu 3-SO4)(H2O)2]middotH2O}n (1), {[Co(Htcpb)(H2O)3]middot0.5CH3CNmiddotH2O}n (2), and {[Ni-(Htcpb)(H2O)3]middotH2O}n (3), based on 2-(6-phenyl-[2,3 '-bipyridin]-4-yl)benzene-1,3,5-tricarboxylic acid (H3tcpb) to study their proton transport pathways and conducting mechanisms. The electrochemical experimental results demonstrated that the finest proton conductivity (Sigma) value of 1 modified by sulfate anions can reach as high as 5.83 x 10-3 Smiddotcm-1 being approximately three times greater than that of H3tcpb-H2O (1.90 x 10-3 Smiddotcm-1). Meanwhile, the finest Sigma values of two isomeric 2 and 3 being 3.14 x 10-3 and 3.08 x 10-3 Smiddot cm-1, respectively, are also higher than the value of H3tcpb-H2O. This report demonstrates that the finest Sigma values of H3tcpb-H2O and 1-3 are all in line with the demand for high-protonic conductors, which sparks us to bring about better proton-conducting crystalline materials.