Ultrafast Luminescent Light-Up Guest Detection Based on the Lock of the Host Molecular Vibration

Light-up luminescence
sensors have been employed in real-time in situ visual
detection of target molecules including volatile
organic compounds (VOCs). However, currently employed light-up sensors,
which are generally based on the aggregation-induced emission (AIE)
or solvent-induced energy transfer effect, exhibit limited sensitivity
for light-up detection and poor recycling performances thereby significantly
hindering their industrial applications. Inspired by the low-temperature
enhanced luminescence phenomenon, we herein propose and show that
a guest-lock-induced luminescence enhancement mechanism can be used
to realize the ultrafast light-up detection of target VOCs. Through
introduction of chlorinated hydrocarbons to lock the molecular vibrations
within a designed [Cu4I4]-based metal–organic
framework (MOF), luminescence intensity could be enhanced significantly
at room temperature. This guest-lock-induced luminescence enhancement
is brought about by weak supramolecular interactions between the host
framework and the guest molecules, allowing highly sensitive and specific
detection of the guest vapor with ultrafast response time (<1 s).
Single-crystal X-ray diffraction (SCXRD) analysis of guest molecules-loaded
MOFs and density functional theory (DFT) calculations were employed
to investigate the host–guest interactions involved in this
phenomenon. Moreover, the above MOF sensor successfully achieved real-time
detection of a toxic chloroaromatic molecule, chlorobenzene. The guest-lock-induced
light-up mechanism opens up a route to discovering high-performance
ultrafast light-up luminescent sensors for real-time detection applications.