Hierarchical porous UIO-66-NH2 derived from ionic liquid enabling sub-second humidity response for respiratory monitoring and non-contact sensing

The controllable pore structures and surface functionalization characteristics of metal-organic frameworks (MOFs) provide new ideas for the development of high-performance humidity sensors. In this study, a hierarchical porous IL/UIO-66-NH 2 material with well-defined microporous-mesoporous channels was successfully synthesized. This unique porous structure results from the steric hindrance effect and competitive coordination of a carboxylic acid-functionalized ionic liquid used as the MOF precursor. By combining the Kelvin equation with Fick's law of diffusion, we revealed how the synergistic interactions within hierarchical pore structures enhance water-molecule transport dynamics, resulting in ultrafast sensor performance with response and recovery times of 0.6 s and 0.9 s, respectively. The humidity sensing mechanism was systematically investigated using electrochemical impedance spectroscopy. The sensor can accurately distinguish respiratory states and recognize short speech signals, providing a new material design strategy for wearable health monitoring devices.