Hydrogen-bond induced enhanced fluorescence sensing of metal organic frameworks for colorimetric l-glutamic acid and l-aspartic acid detection

Fluorescent metal–organic frameworks (FMOFs) hold great promise for detecting biomolecules, but a comprehensive understanding of their response mechanisms is still challenging to guide the design of assays. Herein, we creatively proposed fluorescent analysis via the hydrogen-bond-triggered enhanced fluorescence effect between the oxygen of a carboxyl group of targets and an amino group of ligands in the FMOFs in an aqueous solution. Based on the above strategy, we synthesized the Ru@ZrMOF and constructed a ratiometric fluorescent and colorimetric dual-readout method for a simple and rapid platform to selectively detect amino acids. Taking l -glutamic ( l -Glu) and l -aspartic acid ( l -Asp) as examples, the introduction of l -Glu and l -Asp sharply increased the fluorescent value at 450 nm through strong hydrogen bonding, leading to a difference in the color from red to blue. Data from computational simulations point to the presence of strong hydrogen bonds between l -Glu/ l -Asp and FMOFs. Dual-mode fluorescent/colorimetric method selectively and accurately detects l -Glu acid and l -Asp within 30 min. The detection range for the two was found to be between 5 μM and 2 mM, with detection limits of 3 μM and 2.5 μM, respectively. In addition, a paper-based platform was fabricated and a logic gate was developed for the rapid and visual measurement of l -Glu and l -Asp. This platform is simple, quick, easy to use, and sensitive, making it a promising tool for future applications in amino acid detection, particularly in biological samples.