Engineering Covalent Organic Frameworks with Polyethylene Glycol as Self-Sustained Humidity-Responsive Actuators.

Regarding the global energy crisis, it is of profound significance to develop spontaneous power generators that harvest natural energy. Fabricating humidity-responsive actuators that can conduct such energy transduction is of paramount importance. Herein, we incorporate covalent organic frameworks with flexible polyethylene glycol to fabricate rigid-flexible coupled membrane actuators. This strategy significantly improves the mechanical properties and humidity-responsive performance of the actuators, meanwhile, the existence of ordered structures enables us to unveil the actuation mechanism. These high-performance actuators can achieve various actuation applications and exhibit interesting self-oscillation behavior above a water surface. Finally, after being coupled with a piezoelectric film, the bilayer device can spontaneously output electricity over 2 days. This work paves a new avenue to fabricate rigid-flexible coupled actuators for self-sustained energy transduction.