Proton-Conducting Phenolate-Based Zr Metal–Organic Framework: A Joint Experimental–Modeling Investigation

Abstract

The proton-conduction performances of the chemically stable porous zirconium phenolate MIL-163 MOF were characterized for the first time by complex impedance spectroscopy. Whereas this large square-shaped channel-like MOF exhibits very poor conductivity under anhydrous conditions, measurements performed at 90 °C and 95% relative humidity evidenced a superprotonic behavior with a conductivity of 2.1 × 10 −3 S•cm −1 , among the highest values reported so far for waterstable MOFs. This experimental investigation was further supported by Monte Carlo simulations to shed light on the effects of both the guest molecules (i.e., dimethylamine and water) and the acidic protons from the constitutive inorganic chains on the conduction properties of this porous hybrid solid. It was found that the water molecules form a three-dimensional hydrogen-bond network leading to the formation of multiple pathways that bridge the acidic Zrbonded phenol groups of the organic linker, which act as a proton source. The dimethylamine molecules were revealed to form single hydrogen bonds with H 2 O without leading to a disruption of the water hydrogen-bond network. This offers an optimal situation for the water-mediated transfer of protons over long distances at the origin of the good proton-conducting performance of MIL-163.

A Highly Stable Two‐Dimensional Copper(II) Organic Framework for Proton Conduction and Ammonia Impedance Sensing

“…However,s ome peaks from 9.5 to 258 slightly shift towardlower anglesc ompared with the simulated ones, which showsa ne xpansion of the lattice after absorption of water molecules. Thus, it leads to the optimized protonconductivity for 1 of 1.50 10 À3 Scm À1 .A sl isted in Ta ble 2, althought he optimized conductivity value is smaller than that of severalr ecent MOFs, [38][39][40][41] this value can be compared to that of some previousM OFs under similar tested conditions, [41][42][43][44][45][46] and is remarkably highert han that of four imidazole dicarboxylate-based Co II MOFs and other MOFs. [27,28,47] It is illustrated again that the structural advantage of MOF 1 is the a large amount of uncoordinated carboxylate units between the layers forprotontransfer.…”

Two Highly Stable Proton Conductive Cobalt(II)–Organic Frameworks as Impedance Sensors for Formic Acid

“…Through a large amount of research, it has been found that the proton conductivities of MOFs can be regulated by introducing different components, such as acidic moieties (e.g.,R SO 3 H, H 3 PO 4 ) and extraneous protonic molecules (e.g.,a mine, N-heterocy-cles), into the pores and channels of MOFs. [8,17,18,[25][26][27][28][29][30] Stimulated by this, we hope to apply proton-conductiveM OFs to the sensing of alkaline or acidic gases. Fortunately,w ehave successfully deployed several proton-conductive MOFs as reliable NH 3 sensors.…”

“…Meanwhile, MOFs have been evaluated as promising candidates as new types of crystalline proton‐conducting materials. Through a large amount of research, it has been found that the proton conductivities of MOFs can be regulated by introducing different components, such as acidic moieties (e.g., RSO 3 H, H 3 PO 4 ) and extraneous protonic molecules (e.g., amine, N‐heterocycles), into the pores and channels of MOFs . Stimulated by this, we hope to apply proton‐conductive MOFs to the sensing of alkaline or acidic gases.…”

A robust zirconium amino acid metal-organic framework for proton conduction

“…It is worth mentioning that the porous Zr-amino acids MOF would be of great interest since in general high stability and excellent performance in various applications have been highlighted for Zr-carboxylate MOFs over the last few years 26 . In the field of proton conductive materials, the design of Zr-MOFs based on non-commercially available linkers has been actively investigated, including a flexible tetraphosphonate coordination polymer 27 , a Zr-phosphonate based on glyphosine 28 , 29 , a phenolate-based MOF 30 , and PCMOF20 31 , outperforming in some cases Nafion. However, these MOFs suffer from either a lack of biocompatible character, the use of expensive or poorly environment-friendly chemicals and/or scale-up limitations.…”