Pre‐Crosslinking via MOFs With Coordinatively Unsaturated Metal Sites for Fabricating Macroporous Hydrogels Toward Efficient Atmospheric Water Harvesting

Abstract

ABSTRACT Freshwater scarcity is a global crisis, and sorbent‐based atmospheric water harvesting (SAWH) offers location‐independent water supply, yet developing fast‐kinetic adsorbents remains challenging. In this study, we report an MOF pre‐crosslinking strategy using metal–organic frameworks (MOFs) with unsaturated metal sites to prepare macroporous hydrogels. This strategy alleviates slow water diffusion induced by dense polymer chain stacking in traditional hydrogels. The obtained MOF pre‐crosslinked macroporous hydrogels (MPMHs) use MOF particles as cross‐linking nodes to construct interconnected macroporous networks, whose hydrophilic nanochannels facilitate rapid water transport inside cross‐linking domains. Compared with conventional hygroscopic salt hydrogel composites (HSHCs), MPMMHs exhibit greatly improved sorption–desorption kinetics and superior SAWH performance. MPMH‐101 attains 96% of its saturated water uptake (0.83 g g −1 ) within 30 min at 25°C and 30% RH, desorbs 70% stored water within 20 min at 70°C, and retains stable performance over 50 cycles. It delivers a water yield of 14.50 g g −1 day −1 at 30% RH and 9.70 g g −1 day −1 in outdoor tests which is 2.4 times higher than that of HSHCs. Moreover, this strategy is versatile to various water stable MOFs (MOF‐808(Zr), UiO‐66(Zr)), and polymers low methoxyl pectin (LMP), providing a potential solution for designing next‐generation SAWH adsorbents.