Hydrogen‐Bonded Organic Frameworks (HOFs): A New Class of Porous Crystalline Proton‐Conducting Materials

Abstract

Two porous hydrogen-bonded organic frameworks (HOFs) based on arene sulfonates and guanidinium ions are reported. As a result of the presence of ionic backbones appended with protonic source, the compounds exhibit ultra-high proton conduction values (σ) 0.75× 10(-2) S cm(-1) and 1.8×10(-2) S cm(-1) under humidified conditions. Also, they have very low activation energy values and the highest proton conductivity at ambient conditions (low humidity and at moderate temperature) among porous crystalline materials, such as metal-organic frameworks (MOFs) and covalent organic frameworks (COFs). These values are not only comparable to the conventionally used proton exchange membranes, such as Nafion used in fuel cell technologies, but is also the highest value reported in organic-based porous architectures. Notably, this report inaugurates the usage of crystalline hydrogen-bonded porous organic frameworks as solid-state proton conducting materials.

Metal–Organic Frameworks and Other Crystalline Materials for Ultrahigh Superprotonic Conductivities of 10−2 S cm−1 or Higher

“…demonstrated the effectiveness of such materials for gas sorption and separation applications . Very recently, HOF materials have been explored for their potential usage in proton‐conduction applications . The inherent aspect of hydrogen bonding in HOF materials could be utilized to create effective proton‐conduction pathways by suitably designing the material decorated with donor–acceptor Brønsted acid–base pairs.…”

“…On this basis, Ghosh et al. showed for the very first time how porous HOFs can act as promising proton‐conducting materials by constructing two HOFs that self‐assembled through different arene sulfonates and guanidinium ions as presented in Figure . As a result of the presence of ionic backbones attached to a proton source, both of the HOFs exhibited superprotonic conductivity with values of 0.75×10 −2 and 1.8×10 −2 S cm −1 at 30 °C and 95 % RH.…”

“…[35] Very recently,H OF materials have been explored for their potential usage in proton-conduction applications. [36][37][38] The inherent aspecto fh ydrogen bondingi nH OF materials could be utilized to create effective proton-conduction pathwaysb ys uitably designing the material decorated with donor-acceptor Brønsted acid-base pairs. Such organic crystalline supramolecular frameworks usually exhibit well-ordered structures with an extensive varietyo fh ydrogen bonds between donors and acceptors, which are ultimately necessary for efficient protonconduction.…”

Supramolecular anion recognition in water: synthesis of hydrogen-bonded supramolecular frameworks

“…9 Herein, we describe the use of terephthalate anions to prepare porous frameworks, which we believe to be an unprecedented demonstration of anion-induced self-assembly in water. 10,11 …”

Jumping Crystal of a Hydrogen‐Bonded Organic Framework Induced by the Collective Molecular Motion of a Twisted π System

“…[10] Along with other porous materials,i ncluding zeolite, [11] metal organic framework (MOF), [12] and covalent organic framework (CO-F), [10a, 13] HOFs have been examined for their possible application to gas adsorption. HOFs have been successfully used in various applications,i ncluding separation, [14b, 15] ion conduction, [16] sensor [17] and catalysis. HOFs have been successfully used in various applications,i ncluding separation, [14b, 15] ion conduction, [16] sensor [17] and catalysis.…”