Metal-organic frameworks have great potential in the field of proton conducting materials and fluorescent probes due to their structural tunability and designability. A novel water-stable metal organic framework material [Cd2(Hdpb)(H2O)3]...

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)(H2O)•H2O]n (Co-MOF, L-Glu = L-glutamate) was synthesized by hydrothermal method. Co2+ 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 5 times that of Co-MOF. 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.

The {[Zn(H2PIPZ)](H2O)}n (compound 1) detects Co2+ ions with turn on fluorescent and proton conductivity of composite membrane 1@PVA10 is ten times higher than compound 1 at 98% RH and 353 K.

A water-stable metal-organic framework material of [Cd2 (pbdc)(H2O)3](1) has been synthesized based on H4pbdc (H4pbdc = 5-phosphonobenzene-1,3-dicarboxylic acid) ligands and Cd2+ ions. The Cd2+ ions are interacted with phosphonate and carboxylate groups to form infinitely extending one-dimensional chains, which are then bridged by pbdc ligands to generate a three-dimensional structure. AC impedance study found that the proton conductivity of compound 1 is 2.32 × 10−4 S·cm−1 at 333 K and 98% RH. Many MOF-polymer composite materials have excellent properties (such as heat resistance, high proton conductivity, etc.) and can be used in fuel cells and other fields. Thus, compound 1 was added to the CS matrix to prepare a series of composite membrane 1@CS-X (X = 1%, 3%, 5%, and 7% wt), which have good thermal stability and high proton conductivity. Under the same conditions, the effects of the 1@CS-X composite membranes on proton conduction are better than that of 1, which is caused by the hydrogen bond network constructed between CS and 1, and that provides a continuous channel for proton transfer. Strikingly, the proton conduction value of 1@CS-3 reached 1.10 × 10−2 S·cm −1 353 K and 98% RH, which is much better than many recently reported MOF-polymer composites.

devices to work under tough conditions. There are reports about artificial ATP synthesis and biomimetic power generation through proton gradients. [3] These abiotic ones have potential applications for electronic devices, fuel cell, and chemical sensors. [4] However, significant challenges remain for developing high performance and dynamic regulation of proton conduction. A class of material that is possibly able to improve the proton conduction performance in fuel cells is metal-organic frameworks (MOFs). [5] MOFs are organicinorganic composite porous materials, constructed from metal ions or clusters, and organic ligands through coordination bonds. [6] MOFs have such advantages as high porosity, large specific surface area, and enormous chemical variety. [7]