Bionic Luminescent Sensors Based on Covalent Organic Frameworks: Auditory, Gustatory, and Olfactory Information Monitoring for Multimode Perception

The synthesis of covalent organic frameworks (COFs) with excellent luminescent properties and their effective application in the field of bionic sensing remain a formidable challenge. Herein, a series of COFs with different numbers of hydroxyl groups are successfully synthesized, and the number of hydroxyl groups on the benzene-1,3,5-tricarbaldehyde (BTA) linker influences the properties of the final COFs. The COF (HHBTA-OH) prepared with hydrazine hydrate (HH) and BTA containing one hydroxyl group as the ligands exhibits the best fluorescent performance. MA@HHBTA-OH is formed by the reaction of HHBTA-OH with meldrum's acid (MA) and has its extremely high hydrophilicity, dispersibility, and strong red fluorescence, which can imitate the human gustatory system to detect bitter substances. MA@HHBTA-OH was combined with agarose (AG) to construct a MA@HHBTA-OH@AG film for assessing food freshness. In addition, an acoustic MA@HHBTA-OH@MF sensor is fabricated by integrating luminescent MA@HHBTA-OH with melamine foam (MF) through a strong hydrogen bond. MA@HHBTA-OH@MF functions like an eardrum and recognizes sound through pressure waves with excellent mechanical sensing performance. In summary, biomimetic luminescent sensors based on MA@HHBTA-OH were successfully constructed, which can monitor auditory, gustatory, and olfactory information to achieve the multimode perception of sound, bitter substances, and food freshness.