Water-Stable MIL-MOFs Developed Through a Novel Sacrifice-Protection Strategy Inspired by Butterfly Wings' Scales for...

Metal-organic frameworks, which are the desired candidates for biosensing application due to their tunable properties, are significantly hindered by their rapid degradation in aqueous solutions, as well as the loss of their inherent fluorescence. Most studies aim to improve the hydrophobicity of materials by modifying their contact angle, thereby enhancing water stability. However, water droplets poorly adhere to the surface of hydrophobic materials, limiting their application for direct contact and detection in aqueous environments. Drawing inspiration from the sacrificial protection mechanism of butterfly wings used to evade predation and entanglement, a universal approach is successfully developed to protect water-sensitive MIL-MOFs from water molecule attack while preserving good hydrophilicity. Using the organic ligand 2,2'-bipyridine-5,5'-dicarboxylic acid (bpydc) as sacrificial protection scales, the MIL-125-NH₂-bpydc demonstrated broad pH structural stability (pH 2-12) and fluorescence stability increased by 10.17 time in aqueous solutions, achieving the highest performance in MILMOFs. The MIL-125-NH₂-bpydc is biocompatible enabling it to perform long-term fluorescence imaging in living cells and zebrafish, further detecting hydrogen sulfide (H₂S) in the aqueous and biological systems via turn-on fluorescence emission. This study offers a novel and universal sacrifice-protection strategy for the design and development of the luminescent biocompatible MOFs tailored for biosensing applications.