TY - JOUR
T1 - Designing UiO-66-Based Superprotonic Conductor with the Highest Metal-Organic Framework Based Proton Conductivity
AU - Mukhopadhyay, Subhabrata
AU - Debgupta, Joyashish
AU - Singh, Chandani
AU - Sarkar, Rudraditya
AU - Basu, Olivia
AU - Das, Samar K.
N1 - Publisher Copyright:
Copyright © 2019 American Chemical Society.
PY - 2019/4/10
Y1 - 2019/4/10
N2 - Metal-organic framework (MOF) based proton conductors have received immense importance recently. The present study endeavors to design two post synthetically modified UiO-66-based MOFs and examines the effects of their structural differences on their proton conductivity. UiO-66-NH 2 is modified by reaction with sultones to prepare two homologous compounds, that is, PSM 1 and PSM 2, with SO 3 H functionalization in comparable extent (Zr:S = 2:1) in both. However, the pendant alkyl chain holding the -SO 3 H group is of different length. PSM 2 has longer alkyl chain attachment than PSM 1. This difference in the length of side arms results in a huge difference in proton conductivity of the two compounds. PSM 1 is observed to have the highest MOF-based proton conductivity (1.64 × 10 -1 S cm -1 ) at 80 °C, which is comparable to commercially available Nafion, while PSM 2 shows significantly lower conductivity (4.6 × 10 -3 S cm -1 ). Again, the activation energy for proton conduction is one of the lowest among all MOF-based proton conductors in the case of PSM 1, while PSM 2 requires larger activation energy (almost 3 times). This profound effect of variation of the chain length of the side arm by one carbon atom in the case of PSM 1 and PSM 2 was rather surprising and never documented before. This effect of the length of the side arm can be very useful to understand the proton conduction mechanism of MOF-based compounds and also to design better proton conductors. Besides, PSM 1 showed proton conductivity as high as 1.64 × 10 -1 S cm -1 at 80 °C, which is the highest reported value to date among all MOF-based systems. The lability of the -SO 3 H proton of the post synthetically modified UiO-66 MOFs has theoretically been determined by molecular electrostatic potential analysis and theoretical pK a calculation of models of functional sites along with relevant NBO analyses.
AB - Metal-organic framework (MOF) based proton conductors have received immense importance recently. The present study endeavors to design two post synthetically modified UiO-66-based MOFs and examines the effects of their structural differences on their proton conductivity. UiO-66-NH 2 is modified by reaction with sultones to prepare two homologous compounds, that is, PSM 1 and PSM 2, with SO 3 H functionalization in comparable extent (Zr:S = 2:1) in both. However, the pendant alkyl chain holding the -SO 3 H group is of different length. PSM 2 has longer alkyl chain attachment than PSM 1. This difference in the length of side arms results in a huge difference in proton conductivity of the two compounds. PSM 1 is observed to have the highest MOF-based proton conductivity (1.64 × 10 -1 S cm -1 ) at 80 °C, which is comparable to commercially available Nafion, while PSM 2 shows significantly lower conductivity (4.6 × 10 -3 S cm -1 ). Again, the activation energy for proton conduction is one of the lowest among all MOF-based proton conductors in the case of PSM 1, while PSM 2 requires larger activation energy (almost 3 times). This profound effect of variation of the chain length of the side arm by one carbon atom in the case of PSM 1 and PSM 2 was rather surprising and never documented before. This effect of the length of the side arm can be very useful to understand the proton conduction mechanism of MOF-based compounds and also to design better proton conductors. Besides, PSM 1 showed proton conductivity as high as 1.64 × 10 -1 S cm -1 at 80 °C, which is the highest reported value to date among all MOF-based systems. The lability of the -SO 3 H proton of the post synthetically modified UiO-66 MOFs has theoretically been determined by molecular electrostatic potential analysis and theoretical pK a calculation of models of functional sites along with relevant NBO analyses.
KW - MOF
KW - effect of chain length
KW - humidity-assisted proton conduction
KW - post-synthetic modification
KW - superproton conductors
UR - http://www.scopus.com/inward/record.url?scp=85064131580&partnerID=8YFLogxK
U2 - 10.1021/acsami.9b01121
DO - 10.1021/acsami.9b01121
M3 - Article
C2 - 30888148
AN - SCOPUS:85064131580
SN - 1944-8244
VL - 11
SP - 13423
EP - 13432
JO - ACS Applied Materials and Interfaces
JF - ACS Applied Materials and Interfaces
IS - 14
ER -