Pre-Crosslinking via MOFs With Coordinatively Unsaturated Metal Sites for Fabricating Macroporous Hydrogels Toward...

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.