Controllable Transition Metal-Directed Assembly of Mo2O2S22+Building Blocks into Smart Molecular Humidity-Responsive Actuators

B Li and XZ Duan and DM Cheng and XY Chen and ZX Gao and WB Ren and KZ Shao and HY Zang, JOURNAL OF THE AMERICAN CHEMICAL SOCIETY, 145, 2243-2251 (2023).

DOI: 10.1021/jacs.2c10225

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 Bi8Mo48 through the assembly of Mo2O2S22+ units, transition metals, and flexible phosphonic acid ligands. Bi8Mo48 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 Bi8Mo48 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.

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