A water stable layered Tb(iii) polycarboxylate with high proton conductivity over 10⁻² S cm⁻¹ in a wide temperature range

Abstract

An unprecedented Tb(iii) polycarboxylate, {[Tb4(TTHA)2(H2O)4]·7H2O}n (1), has been synthesized.

Metal-Organic Frameworks: Synthetic Methods and Potential Applications

“…For example, {H[(N(CH 3 ) 4 ) 2 ][Gd 3 (NIPA) 6 ]}·3H 2 O (H 2 NIPA = 5-nitroisophthalic acid) displays high proton conductivity of 7.17 × 10 −2 S·cm −1 at high relative humidity, which is among the highest values for proton-conducting MOFs [ 235 ], and the bimetallic complex {NH(prol) 3 }[MnCr(ox) 3 ] (NH(prol) 3 + = tri(3-hydroxypropyl)ammonium, ox = oxalate), which consists of oxalate-bridged bimetallic layers interleaved by NH(prol) 3 + ions and shows proton conduction of ~10 −4 S·cm −1 under 75% relative humidity due to the presence of an extensive H-bonded network between the anionic MOF, the NH(prol) 3 + ions, and water molecules [ 236 ]. Some examples of neutral MOFs, which display high proton conductivity, are [Tb 4 (TTHA) 2 (H 2 O) 4 ]·7H 2 O (H 6 TTHA = 1,3,5-triazine-2,4,6-triamine hexaacetic acid) with high proton conductivity over 10 −2 S·cm −1 at 295–358 K temperature range due to an extensive H-bond network formed between water solvates and carboxyl groups [ 237 ], [Ln(L)(H 2 O) 2 ] (Ln III = Dy, Er, Gd; H 3 L = (HO) 2 P(O)CH 2 CO 2 H) with proton conductivity values of 1.13 × 10 −6 , 2.73 × 10 −3 , and 6.27 × 10 −6 S·cm −1 , respectively, at high temperatures (>348 K) and 95% relative humidity [ 238 ], and [Ln 2 (CO 3 )(ox) 2 (H 2 O) 2 ]·3H 2 O (Ln III = Ce, Pr, Nd, Tb) with proton conductivity above 10 −3 S·cm −1 without an additional humidity ( Figure 8 ) [ 239 ].…”

Metal–Organic Frameworks as a Versatile Platform for Proton Conductors

“…The high surface areas, rich structural tunability, and functional pore surface of MOFs provide great opportunities to load a variety of guest molecules as proton carriers and to systemically modify the proton concentration and mobility within the available spaces ( Scheme ). [ 27–33 ] In addition, the crystalline nature of MOFs endows an opportunity to investigate the proton transport pathway and mechanism, which will provide theoretical guidance for the design and synthesis of novel proton‐conducting materials. Until now, generally including four types (types I to IV) of strategies have been proposed to regulate the proton conductivity of crystalline porous materials.…”

Theoretical hydrogen bonding calculations and proton conduction for Eu(iii)-based metal–organic framework

“…¼ 7.17 Â 10 À2 S cm À1 , 75 C, 98% RH), 10 À2 S cm À1 , 90 C, 90% RH) 11 and {[Tb 4 (TTHA) 2 (H 2 O) 4 ]$7H 2 O} n (s ¼ 2.57 Â 10 À2 S cm À1 , 60 C, 98% RH)12 that showing ultrahigh conductivities (>10 À2 S cm À1 ). These superprotonic conductors provided advantageous supports for the assembly strategies involved Ln(III) ion and carboxylate ligand.…”

“…Â 10 À3 S cm À1 , 98% RH, 80 C),26 [Nd(mpca) 2 Nd(H 2 O) 6 Mo(CN) 8 ]$ nH 2 O (s ¼ 2.8 Â 10 À3 S cm À1 , 98% RH, 80 C),27 MFM-550(M) and MFM-555(M) (M ¼ La, Ce, Nd, Sm, Gd, Ho) (s ¼ 1.46 Â 10 À6 to 2.97 Â 10 À4 S cm À1 , 99% RH, 20 C)28 as well as other conductive materials showing lower conductivities in the range of 10 À9 to 10 À5 S cm À1 9. However, the conductivity of 1 is inferior to those Ln(III)-MOFs with conductivities higher than 10 À2 S cm À1 Â[10][11][12] In O} n 19b have been previously reported by our group, which show highest proton conductivities of 2.57 Â 10 À2 S cm À1 at 60 C and 8.79 Â 10 À4…”

“…Therefore, the carboxylate-bridged Ln( iii )-MOF are good candidates for proton conduction. 9 Currently, there are several proton conductive MOF materials, such as {H[(N(Me) 4 ) 2 ][Gd 3 (NIPA) 6 ]}·3H 2 O ( σ = 7.17 × 10 −2 S cm −1 , 75 °C, 98% RH), 10 Na 2 [Eu(SBBA) 2 (FA)]·0.375DMF·0.4H 2 O ( σ = 2.91 × 10 −2 S cm −1 , 90 °C, 90% RH) 11 and {[Tb 4 (TTHA) 2 (H 2 O) 4 ]·7H 2 O} n ( σ = 2.57 × 10 −2 S cm −1 , 60 °C, 98% RH) 12 that showing ultra-high conductivities (>10 −2 S cm −1 ). These superprotonic conductors provided advantageous supports for the assembly strategies involved Ln( iii ) ion and carboxylate ligand.…”