Proton Transport through Robust CPO-27-type Metal Organic Frameworks

Abstract

In this work we studied the robustness of Ni-CPO-27 and Mg-CPO-27 metal organic frameworks (MOFs) upon cold uniaxial pressing and thermal cycling in dry and wet Ar/H2. The preparation and operation limits for each material are found to be 225 and 150 MPa and temperatures of 250 and 150 °C for Ni-CPO-27 and Mg-CPO-27, respectively. The electrochemical alternating current conductivity measurements performed as high as 250 °C showed conductivity values ranging from 10–6 to 10–8 S/cm, depending on the material, temperature, and atmosphere. The protonic nature of the electrochemical transport phenomena was unambiguously confirmed via proton/deuteron isotopic and transient hydration studies. The study reveals high reproducibility and stability of the electrochemical measurements upon cycling in different atmospheres. Meanwhile, the crystallinity of the sample was preserved after the conductivity study and three weeks on stream, which demonstrates the midterm stability and robustness of this MOF.

Understanding the Formation Mechanism of Metal Nanocrystal@MOF-74 Hybrids

“…As it is well-known that MOF-74 is a widely used framework material due to its excellent chemical robustness and thermal stability. − Based on the profiles of TGA analysis (Figure S5), the framework decomposition starts at about 350 °C for the Cu@Cu-MOF-74, which is in good agreement with the as-prepared pure Cu-MOF-74 …”

“…The system selection was dictated by the following. With regards to the choice of the Cu as metal: (1) Cu NCs are active catalysts for many high temperature gas phase reactions, such as methane production and methanol synthesis from CO 2 , as well as electrochemical CO 2 reduction. − (2) To date, only a few examples of Cu NCs embedded in framework materials have been reported and these are grown by chemical vapor infiltration. − (3) The as-synthesized Cu@MOF-177, Cu@MOF-5, and Cu/ZnO@MOF-5 have shown decent activity as catalysts for methanol synthesis. − With regards to the choice of the framework material, M-MOF-74 (alternatively known as M 2 (dobdc), CPO-27-M, or M 2 (dhtp), where M = Mg, Mn, Fe, Co, Ni, Cu, or Zn) constitutes an extensive framework family with extreme chemical versatility and thermal and chemical stability, allowing for a wide variety of applications ranging from gas storage and separations to ion conductivity and catalysis. − The M-MOF-74 structure type consists of one-dimensional metal oxide chains that are connected by 2,5-dioxido-1,4-benzene-dicarboxylate (dobdc 4– ) ligands to form a hexagonal array of one-dimensional channels . Upon heating the material under dynamic vacuum a solvent molecule is freed from each metal, leaving behind open-coordination sites that point into the channel, a structural feature shown to induce selectivity in the adsorption of small guest molecules and also to facilitate chemical reactions on the framework surface. , It is hypothesized that the creation of metal NC@M-MOF-74 hybrids can promote synergistic effects as the framework can provide size and shape selectivity of guest molecules, concentrate guest molecules around the catalysts, and also promote the activation of the guest molecules, allowing the MOF to play a direct role in the catalytic process and/or enhance the catalytic behavior of the metallic NCs. − , Despite the intrinsic potential of NC@MOF-74 hybrids, only a few examples have been reported so far in the literature. , In one example, Ni@Ni-MOF-74 hybrids were obtained by a one step procedure wherein Ni-MOF-74 was treated at high temperature (350 ° C for 12 h) to form aggregated, polydispersed Ni NCs within the framework …”

Solvent-Induced Change of Electronic Spectra and Magnetic Susceptibility of CoII Coordination Polymer with 2,4,6-Tris(4-pyridyl)-1,3,5-triazine

“…Coordination compounds with porous crystal lattices, the so-called metal–organic frameworks (MOFs) or porous coordination polymers (PCPs), have been attracting attention as a basis for creation of multifunctional materials due to their ability to adsorb or release guest molecules in combination with other properties, which is promising for practical application . Combination of the porosity with accessible paramagnetic ions or luminescent fragments gives rise to creation of porous magnetic or luminescent materials, respectively; pore filling by guests with labile protons allows researchers to develop systems with high proton conductivity, etc. PCPs are also considered as promising size-selective catalysts, selective sorbents, carriers for chromatography, etc.…”

Dense Dithiolene Units on Metal–Organic Frameworks for Mercury Removal and Superprotonic Conduction

“…Free-standing thiol groups anchored on an open framework (e.g., MOF or COF) − represent a powerful platform for advancing materials science, − as is shown in catalysis, , heavy metal removal, − and proton transport studies. − This last direction is of note because very dense −SO 3 H arrays can be achieved to promote proton conductivity simply by oxidizing the thiol precursors on the MOF host. , In this connection, the rich reactivity of the thiol function intersects fruitfully with the key development of using Zr­(IV) , and other hard metal ions [Cr­(III), Al­(III), and Eu­(III)] − for metal–organic framework (MOF) construction. On the one hand, these highly charged cations bond strongly with the carboxyl linkers to stabilize the resulting framework (e.g., against water).…”