TY - JOUR
T1 - Moisture-triggered proton conductivity switching in metal-organic frameworks
T2 - role of coordinating solvents
AU - Lee, Hong Kyu
AU - Oruganti, Yasaswini
AU - Lee, Jonghyeon
AU - Han, Seunghee
AU - Kim, Jihan
AU - Moon, Dohyun
AU - Kim, Min
AU - Lim, Dae Woon
AU - Moon, Hoi Ri
N1 - Publisher Copyright:
© 2024 The Royal Society of Chemistry.
PY - 2023/12/9
Y1 - 2023/12/9
N2 - Metal-organic frameworks are a good platform for investigating the correlation of structures with physical properties due to the facile coordination environment changes and their responsive structures to external stimuli such as pressure, temperature, and gas sorption. In this study, we report a proton conductivity switching behavior in Zn5FDC, [Zn5(μ3-OH)2(FDC)4(solvent)2] (FDC = 9H-fluorene-2,7-dicarboxylate) triggered by relative humidity (RH). Interestingly, depending on the presence and absence of coordinating molecules the MOFs show distinctively different tendencies in their proton conductivity. Two isostructural Zn5FDC compounds, [Zn5(μ3-OH)2(DEF)2(FDC)4] (Zn5FDC-DEF) and [Zn5(μ3-OH)2(FDC)4] (Zn5FDC-OMS; OMS = open metal site), are prepared, in which the three-dimensional connectivities are identical, but the local structures in the secondary building units (SBUs) are different. In the measurement of humidity-dependent conductivity, both MOFs show a dramatic proton conductivity switching phenomenon (ON/OFF ratio, approximately 108), but the conductivity switching occurs at different RHs for each MOF (above RH 70% in Zn5FDC-DEF, and above RH 90% in Zn5FDC-OMS at 298 K). During this process water coordination in metal centers leads to their structural transformation into Zn5FDC-H2O, which means that the different coordination structures by the absence/presence of coordination solvents provide different water access environments to metal centers. The computational calculation supports that the structural transformation of Zn5FDC-OMS triggered by moisture exposure occurred under higher relative humidity conditions than simple coordination solvent replacement in Zn5FDC-DEF. This study proves that the coordination solvents play a role in conductivity variation, and it provides a new design strategy for functional solid-state proton conductors.
AB - Metal-organic frameworks are a good platform for investigating the correlation of structures with physical properties due to the facile coordination environment changes and their responsive structures to external stimuli such as pressure, temperature, and gas sorption. In this study, we report a proton conductivity switching behavior in Zn5FDC, [Zn5(μ3-OH)2(FDC)4(solvent)2] (FDC = 9H-fluorene-2,7-dicarboxylate) triggered by relative humidity (RH). Interestingly, depending on the presence and absence of coordinating molecules the MOFs show distinctively different tendencies in their proton conductivity. Two isostructural Zn5FDC compounds, [Zn5(μ3-OH)2(DEF)2(FDC)4] (Zn5FDC-DEF) and [Zn5(μ3-OH)2(FDC)4] (Zn5FDC-OMS; OMS = open metal site), are prepared, in which the three-dimensional connectivities are identical, but the local structures in the secondary building units (SBUs) are different. In the measurement of humidity-dependent conductivity, both MOFs show a dramatic proton conductivity switching phenomenon (ON/OFF ratio, approximately 108), but the conductivity switching occurs at different RHs for each MOF (above RH 70% in Zn5FDC-DEF, and above RH 90% in Zn5FDC-OMS at 298 K). During this process water coordination in metal centers leads to their structural transformation into Zn5FDC-H2O, which means that the different coordination structures by the absence/presence of coordination solvents provide different water access environments to metal centers. The computational calculation supports that the structural transformation of Zn5FDC-OMS triggered by moisture exposure occurred under higher relative humidity conditions than simple coordination solvent replacement in Zn5FDC-DEF. This study proves that the coordination solvents play a role in conductivity variation, and it provides a new design strategy for functional solid-state proton conductors.
UR - http://www.scopus.com/inward/record.url?scp=85180597304&partnerID=8YFLogxK
U2 - 10.1039/d3ta06197c
DO - 10.1039/d3ta06197c
M3 - Article
AN - SCOPUS:85180597304
SN - 2050-7488
VL - 12
SP - 795
EP - 801
JO - Journal of Materials Chemistry A
JF - Journal of Materials Chemistry A
IS - 2
ER -
