A Dual-Function Cobalt Metal-Organic Framework for High Proton Conduction and Selective Luminescence Sensing of Histidine

Proton exchange membrane (PEM) is a key component of proton exchange membrane fuel cells (PEMFCs). In recent years, metal organic framework (MOF) and its composite membranes have become the research hotspots. [Co(L-Glu)(H 2 O)·H 2 O] n (Co-MOF, L-Glu = L-glutamate) was synthesized by hydrothermal method. Co 2+ ions are coordinated with L-Glu ligands and water molecules to form one-dimensional chains extending along the a- axis, which are further bridged by L-Glu ligands to form a three-dimensional network structure. AC impedance analysis shows that the proton conductivity of Co-MOF reaches 3.14 × 10 −4 S·cm −1 under 98% relative humidity (RH) and 338 K. To improve proton conductivity, different contents of Co-MOF were added in chitosan (CS) to form composite membranes Co-MOF@CS-X (mass fraction X = 5%, 10%, 15% wt). The results show the proton conductivity of the Co-MOF@CS-10 composite membrane is 1.73 × 10 −3 S·cm −1 at 358 K and 98% RH, which is more than 3 times that of pure CS. As far as we known, this is the first composite made of amino acid MOFs and CS as proton exchange membrane. Furthermore, Co-MOF has an obvious quenching effect on L-histidine in aqueous solution, which can detect the content of L-histidine in water with high sensitivity, and the detection limit is 1 × 10 −7 M.