Thermal-responsive PNIPAM/UiO-66 aerogels for controllable water capture and release

Developing metal–organic framework (MOF)-based sorbents with high water-uptake capacity and mild regeneration conditions remains challenging, but is highly sought after for addressing water shortages. Herein, we report a strategy for fabricating thermal-responsive Poly (N-isopropylacrylamide) (PNIPAM)/UiO-66 composite aerogels with variable PNIPAM loading by leveraging the ordered nanopores of UiO-66 colloids, enabling the confined polymerization of NIPAM monomers within the pores, which allows for controllable water capture and release at above 32 ℃. The thermal-responsive PNIPAM/UiO-66 composite aerogels, with varying PNIPAM loadings, demonstrated an outstanding maxima water capture of over 2100 wt% at room temperature and reversible release at above 32 ℃. This performance sets a new benchmark for the leading water-capture adsorbents reported in the literature, thanks to the extensive specific surface area of the aerogels and the unique hydrophilicity-hydrophobicity transition exhibited by the PNIPAM component. More intriguingly, the aforementioned phase transition can be directly visualized by incorporating 4-(1,2,2-triphenylvinyl) benzoic acid (TPE-COOH) molecules with the well-known aggregation-induced emission (AIE) effect into the aerogels. The remarkable water-uptake ability and mild release conditions showcased in this study open new possibilities for practical water harvesting.