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

Abstract

ABSTRACT 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.