Selective Encapsulation of Ionic Liquids in UiO-66-NH2 Nanopores for Enhanced Humidity Sensing

Metalorganic frameworks (MOFs) with certain pore structures arebeneficial for encapsulating small molecules and realizing functionalapplications. In this work, ionic liquids (ILs) with similar chemicalstructures and different molecular sizes were in situ encapsulated in UiO-66-NH2 nanopores in the synthesisprocess. IL with a molecular size comparable to UiO-66-NH2 nanopores could be effectively encapsulated. The prepared ILs@MOF-basedsensor shows good sensing performance in the relative humidity (RH)range (5-95%) with a small humidity hysteresis of 1.0% RH andgood stability, and found the response value is closely related tothe IL encapsulated amount. The multifunctional applications of theoptimized sensor in human breath, skin humidity, and low humiditydetection were explored. This work proves the importance of size selectionin preparing ILs@MOF nanomaterials with low leakage risk for specificfunctionalization.

Automated summary

In this work, ionic liquids (ILs) were encapsulated in UiO-66-NH2 nanopores to create ILs@MOF nanomaterials. The resulting ILs@MOF-based sensor exhibited good sensing performance with a small humidity hysteresis and good stability. The sensor's response value was closely related to the amount of IL encapsulated. The study also demonstrated the multifunctional applications of the optimized sensor in human breath, skin humidity, and low humidity detection.