Smart molecular actuators have become
a cutting-edge
theme due
to their ability to convert chemical energy into mechanical energy
under external stimulations. However, realizing actuation at the molecular
level and elucidating the mechanisms for actuating still remain challenging.
Herein, we design and fabricate a novel nanoscaled polyoxometalate-based
humidity-responsive molecular actuator {Bi
8
Mo
48
} through
the assembly of [Mo2O2S2]2+ units, transition metals, and flexible phosphonic acid ligands.
{Bi
8
Mo
48
} exhibits a semi-flexible cage-like architecture
with oxygen-rich surfaces and highly negative charges 72–.
The nanoscaled molecular actuator shows reversible expansion and contraction
behavior under humidity variations due to lattice expansion and contraction
induced by hydrogen bonding and solvation interactions between {Bi
8
Mo
48
} and water molecules. Molecular dynamics simulation was further
employed to study these processes, which provides a fundamental understanding
for the mechanism of humidity actuation at the molecular level.
Two kinds of octamolybdate-based Ni II -coordination polymers were synthesized by hydrothermal methods:The Single crystal X-ray diffraction indicates that compounds 1 and 2 are the 2D layer based on γ-[Mo 8 O 26 ] 4À type and a 1D chain based on β-[Mo 8 O 26 ] 4À type polyoxomolybdate anions, respectively. At 85 °C and 98 % RH, the optimal conductivities of the two compounds are 1.03 × 10 À 2 S cm À 1 and 1.12 × 10 À 2 S cm À 1 , respectively. They exhibit good proton conductivity due to the rich imidazole units as carriers and continuous hydrogen bond networks as proton transport pathway. In this work, two molybdate-based proton conducting materials are designed. [a] W.-B.
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