4D-Printed Dual-Functional Hydrogels Breaking the Trade-Off Between Rapid Kinetics and Ultrahigh Water Uptake for Atmospheric Water Harvesting

Sorption-based Atmospheric Water Harvesting (AWH) is an innovative approach to mitigate global freshwater scarcity. However, there is a trade-off between rapid kinetics and ultrahigh water uptake, which is a formidable challenge in designing sorbent materials. Herein, 4D printed dual-functional hydrogel is constructed through the collaborative design of molecular-scale dynamic response network and macro-scale structure. The 4D dual-functional hydrogel integrates thermoresponsive (PNIPAM) and zwitterionic (PDMPAS) to form dynamic response networks, and is loaded with polypyrrole (PPY) and lithium chloride (4D TZG-PPY-LiCl). Simultaneously, 4D TZG-PPY-LiCl utilizes an abundant air-sorbent interface to accelerate moisture absorption kinetics, exhibiting a large swelling ratio under humidity stimulation to capture more water. The moisture absorption rate and water uptake of 4D TZG-PPY-LiCl are double those of bulk TZG-PPY-LiCl between 30% and 90% RH, exhibiting an ultrahigh water uptake of 1.62–6.85 g g⁻¹, which is superior to that of the state-of-the-art sorbents. In addition, the excellent photothermal conversion of 4D TZG-PPY-LiCl induces a hydrophilic to hydrophobic transition and structural shrinkage under one-sun illumination, facilitating rapid water release. Furthermore, 4D TZG-PPY-LiCl AWH device has been further constructed, enabling continuous freshwater production. This breakthrough provides a new idea for the development of sorbent materials.