Proton‐Conductive 3D Ln^III Metal–Organic Frameworks for Formic Acid Impedance Sensing

Abstract

Metal-organic frameworks (MOFs) as new classes of proton-conducting materialsh ave been highlighted in recent years. Nevertheless, the exploration of proton-conducting MOFs as formic acid sensors is extremelyl acking. Herein, we prepared two highly stable 3D isostructurall anthanide(III) MOFs, {(M(m 3 -HPhIDC)(m 2 -C 2 O 4 ) 0.5 (H 2 O))·2 H 2 O} n (M = Tb (ZZU-1); Eu (ZZU-2)) (H 3 PhIDC = 2-phenyl-1H-imidazole-4,5-dicarboxylic acid), in which the coordinated and uncoordinated water molecules and uncoordinated imidazole Na toms play decisive roles for the high-performancep roton conductiona nd recognition ability for formic acid.B oth ZZU-1 and ZZU-2 showt emperature-and humidity-dependent proton-conducting characteristics with high conductivities of 8.95 10 À4 and 4.63 10 À4 Scm -1 at 98 %R Ha nd 100 8C, respectively.I mportantly,t he impedance values of the two MOF-based sensors decrease upon exposure to formica cid vapor generated from formic aqueous solutions at 25 8Cw ith good reproducibility.B yc omparing the changes of impedance values, we can indirectly determine the concentration of HCOOHi na queous solution.T he results showedt hat the lowest detectablec oncentrations of formic acid aqueous solutions are 1.2 10 À2 mol L À1 by ZZU-1 and 2.0 10 À2 mol L À1 by ZZU-2.F urthermore,t he two sensors can distinguish formic acid vapor from interfering vapors including MeOH, N-hexane, benzene, toluene, EtOH, acetone,a cetic acid and butane. Our research provides a new platform of proton-conductive MOFs-based sensors for detecting formic acid.[a] R.

Bi(iii) MOFs: syntheses, structures and applications

“…[1][2][3][4] Moreover, the most prominent advantage of MOFs is that their structures can be regulated and controlled during or after synthesis. 5 So far, MOFs have been widely used in catalysis, 6,7 fluorescence, [8][9][10][11][12] gas adsorption, [13][14][15] proton conduction, [16][17][18][19][20] sensors [21][22][23][24] and so on. In recent years, the research of MOFs has advanced rapidly, and thousands of MOFs have been syn- 39 They used MeOH to dissolve Bi(NO 3 ) 3 •5H 2 O and the 2-pyridinecarbaldehyde isonicotinoylhydrazone (Hpcih) ligand in the two arms of the branch tube and sealed the tube.…”

Switched Proton Conduction in Metal–Organic Frameworks

“… 89 Li’s group observed the proton-conducting response to formic acid vapor in two 3D isostructural Ln(III) MOFs, ZZU-1 and ZZU-2. 90 They can distinguish formic acid vapor from other organic small-molecule vapors such as methanol, ethanol, acetone, toluene, acetic acid, etc. It may be concluded that only formic acid can form hydrogen bonds with H 2 O and imidazole, ascribed to the large polarity (in comparison with hydrocarbons, alcohols, or ketones) and small volume (in comparison with acetic acid) of formic acid.…”

Mechanistic Insight into Charge and Energy Transfers of Luminescent Metal–Organic Frameworks Based Sensors for Toxic Chemicals

“…Formic acid sensing was stabilized by H-bond formation between the imidazole nitrogen-linked MOFs and formic acid. [209] The better geometrical and luminescence properties of lanthanides MOFs could be due to the metal center possessing 4f-electrons. [210] Toluene is hazardous and carcinogenic, with exposure causing adverse health effects.…”