Single Crystal Proton Conduction Study of a Metal Organic Framework of Modest Water Stability

Abstract

A sulfonated indium (In) metal organic framework (MOF) is reported with an anionic layered structure incorporating hydrogen-bonded dimethylammonium cations and water molecules. The MOF becomes amorphous in >60% relative humidity; however, impedance analysis of pelletized powders revealed a proton conduction value of over 10 S cm at 25 °C and 40% RH, a very high proton conduction value for low humidity and moderate temperature. Given the modest humidity stability of the MOF, triaxial impedance analyses on a single crystal was performed and confirmed bulk proton conductivity over 10 S cm along two axes corroborating the data from the pellet.

A Phosphate‐Based Silver–Bipyridine 1D Coordination Polymer with Crystallized Phosphoric Acid as Superprotonic Conductor

“…These species create a push–pull mechanism for proton conduction . The observed conductivity of 3.3×10 −3 S cm −1 (95 % RH, 80 °C) is comparable to those of reported MOFs/CPs: Fe(ox) ⋅ 2 H 2 O (1.3×10 −3 S cm −1 , 25 °C, 98 % RH), H 3 PO 4 @MIL‐101 (3×10 −3 S cm −1 , 150 °C, 0.13 % RH), (NH 4 ) 2 (adp)[Zn 2 (ox) 3 ] ⋅ 3 H 2 O (8×10 −3 S cm −1 , 25 °C, 98 % RH), (NH 4 ) 4 [MnCr 2 (ox) 6 ] 3 ⋅ 4 H 2 O (1.1×10 −3 S cm −1 , 25 °C, 98 % RH), Co‐fdc (4.85×10 −3 S cm −1 , 80 °C, 98 % RH), PCMOF‐5 (2.5×10 −3 S cm −1 , 60 °C, 98 % RH), UiO‐66(Zr)‐(CO 2 H) 2 (2.3×10 −3 S cm −1 , 90 °C, 95 % RH), His@[Al(OH)(1,4‐ndc)] (1.7×10 −3 S cm −1 , 150 °C, 0 % RH), NENU‐530 (1.5×10 −3 S cm −1 , 75 °C, 98 % RH), β‐PCMOF2 (1.3×10 −3 S cm −1 , 85 °C, 90 % RH), MgH 6 ODTMP ⋅ 6 H 2 O (1.5×10 −3 S cm −1 , 19 °C, 100 % RH), Co II [Cr III (CN) 6 ] 2/3 ⋅ 4.2 H 2 O (1.7×10 −3 S cm −1 , 35 °C, 100 % RH), Ti IV Ti IV (HPO 4 ) 4 (1.2×10 −3 S cm −1 , 25 °C, 95 % RH), [Zn 3 (H 2 PO 4 ) 6 ](Hbim) (1.3×10 −3 S cm −1 , 120 °C, 0 % RH), MFM‐512 (2.9×10 −3 S cm −1 , 25 °C, 99 % RH) and PCMOF‐17 single crystal (1.17×10 −3 S cm −1 , 25 °C, 40 % RH) (Table S3, Supporting Information) …”

Proton Conductivity of Composite Polyelectrolyte Membranes with Metal‐Organic Frameworks for Fuel Cell Applications

“…Proton conductivity properties of MOFs have been deeply investigated during the last 10 years by means of two‐ or four‐electrode impedance spectroscopy over different conditions of relative humidity and temperatures. Intrinsic proton conductivity measurements are limited to isolated studies carried out on single crystals when available . Otherwise, bulk conductivity of powdered pellets is normally reported and it takes into account both the intrinsic average conductivity and the surface conductivity effects due to the interparticle contacts.…”

Metal–Organic Frameworks as a Versatile Platform for Proton Conductors

“…So far, the measurement of AC impedance spectra of CPs/MOFs‐based proton conductors has been carried out almost exclusively on the pelleted samples, and only a small number of reported MOFs were tested by using the single‐crystal or nanofilm samples. [ 138–142 ] Although the measurement of pelleted samples is beneficial to provide macroscopic proton conducting properties of one material, it is difficult to reveal the inherent proton conduction mechanism. In order to investigate the anisotropic proton conduction behavior of CPM‐based proton conductors, Kim and co‐workers [ 143 ] realized the first example of porous organic molecule by employing the single‐crystal sample in 2011.…”