A stable porphyrinic metal–organic framework pore-functionalized by high-density carboxylic groups for proton conduction

Metal-organic frameworks (MOFs) have been extensively exploreda sa dvanced chemical sensors in recent years. However,t here are few studies on MOFs as acidic gas sensors, especiallyp rotonc onductive MOFs.I nt his work, two new proton-conducting 3D MOFs,{ [Co 3 (p-CPhHIDC) 2 (4,4'-bipy)(H 2 O)]·2H 2 O} n (1)( p-CPhH 4 IDC = 2-(4-carboxylphenyl)-1 H-imidazole-4,5-dicarboxylic acid;4 ,4'-bipy = 4,4'-bipyridine) and {[Co 3 (p-CPhHIDC) 2 (bpe)(H 2 O)]·3H 2 O} n (2) (bpe = trans-1,2-bis(4-pyridyl)ethylene) have been solvothermally prepared and investigated their formic acid sensing properties. Both MOFs 1 and 2 show temperature-and humidity-dependent protonc onductive properties and exhibit optimizedp roton conductivities of 1.04 10 À3 and 7.02 10 À4 Scma t9 8% relative humidity (RH) and 100 8C, respectively.T he large number of uncoordinated carboxylic acid sites, free and coordination water molecules, andh ydrogen-bondingn etworks inside the frameworks are favorable to the proton transfer.B ym easuringt he impedance values after exposure to formic acid vapor at 98 %o r6 8% RH and 25 8C, both MOFs indicater eproducibly high sensitivity to the analyte. The detection limit of formic acid vapor is as low as 35 ppm for 1 and 70 ppm for 2.M eanwhile, both MOFs also show commendable selectivity towards formic acid among interfering solutions. The proton conducting and formic acid sensingm echanismsh ave been suggested according to the structural analysis, E a calculations, N 2 and water vapor absorptions, PXRD and SEM measurements. This work will open an ew avenue for proton-conductive MOFbased impedance sensors and promote the potentiala pplication of these MOFs fori ndirectly monitoring the concentrationsofformic acid vapors.[a] R.

Section: Introductionmentioning

confidence: 88%

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

Liu

Shi

Wang

et al. 2019

“…All of them, except for the material described in, include the nickel(II) porphyrinylphosphonate (Ni‐H 8 TPPP) as an organic moiety, and only one MOF possesses a moderate proton conductivity . In general, there are few examples of proton‐conductive MOFs based on porphyrins . Therefore, the development of an efficient strategy towards MOFs based on porphyrinylphosphonates with proton conductivity is a particularly important scientific challenge.…”

Section: Methodsmentioning

confidence: 99%

“…[36] In general, there are few examples of proton-conductive MOFs based on porphyrins. [38][39][40] Therefore, the developmento fa ne fficient strategy towards MOFs based on porphyrinylphosphonates with proton conductivity is ap articularly important scientific challenge.Here, we present an ew originals ynthetic approach towards high proton-conductive nickel(II) porphyrinylphosphonate basedM OF [Zn 3 (Ni…”

mentioning

confidence: 99%

Highly Proton‐Conductive Zinc Metal‐Organic Framework Based On Nickel(II) Porphyrinylphosphonate

Enakieva

Sinelshchikova

Grigoriev

et al. 2019

The design of new solid‐state proton‐conducting materials is a great challenge for chemistry and materials science. Herein, a new anionic porphyrinylphosphonate‐based MOF (IPCE‐1Ni), which involves dimethylammonium (DMA) cations for charge compensation, is reported. As a result of its unique structure, IPCE‐1Ni exhibits one of the highest value of the proton conductivity among reported proton‐conducting MOF materials based on porphyrins (1.55×10−3 S cm−1 at 75 °C and 80 % relative humidity).

“…Li et al reported ah ighly stable porphyrine-ring-based 3D Co-MOF that contained open channels decorated with ahigh density of uncoordinated ÀCOOH groups. [25] It exhibited ultra-high proton-conducting behavior at very high RH, thus indicating its highly humidity-dependent proton-conductingn ature. Owing to the presence of large numberso ff ree ÀCOOH groups,t he protons hop forward along the hydrogen bonds formed by water molecules at high humidity.This MOF exhibits exceptional stabilityand conduction robustnesswith aconductivity value of 3.9 10 À2 Scm À1 at 95 %R Ha nd 80 8C.…”

Section: Conceptmentioning

confidence: 98%

“…Li et al. reported a highly stable porphyrine‐ring‐based 3D Co‐MOF that contained open channels decorated with a high density of uncoordinated −COOH groups . It exhibited ultra‐high proton‐conducting behavior at very high RH, thus indicating its highly humidity‐dependent proton‐conducting nature.…”

Section: Intoductionmentioning

confidence: 99%

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

Chand

Elahi

Pal

et al. 2019

118

111

Proton‐conducting materials in the solid state have received immense attention for their role as electrolytes in proton‐exchange membrane fuel cells. Recently, crystalline materials—metal–organic frameworks (MOFs), hydrogen‐bonded organic frameworks (HOFs), covalent organic frameworks (COFs), polyoxometalates (POMs), and porous organic crystals—have become an exciting research topic in the field of proton‐conducting materials. For a better electrolyte, a high proton conductivity on the order of 10−2 S cm−1 or higher is preferred as efficient proton transport between the electrodes is ultimately necessary. With an emphasis on design principles, this Concept will focus on MOFs and other crystalline solid‐based proton‐conducting platforms that exhibit “ultrahigh superprotonic” conductivities with values in excess of 10−2 S cm−1. While only a handful of MOFs exhibit such an ultrahigh conductivity, this quality in other systems is even rarer. In addition to interpreting the structural–functional correlation by taking advantage of their crystalline nature, we address the challenges and promising directions for future research.