A pH-regulated fluorescence covalent organic framework for quantitative water content detection in methanol

In this paper, we designed and synthesized a two-dimensional fluorescent covalent organic framework (TAPB-DMTP-COF) for the precise determination of H₂O content in methanol. The COF was synthesized using two typical monomers by grinding method, which significantly reduced the synthesis time. By adjusting the pH value of the COF suspension to 4.0, the portion of the COF material structure is disrupted, thereby mitigating π-π stacking and resolving the aggregation-caused quenching (ACQ) effect. Consequently, the non-fluorescent TAPB-DMTP-COF exhibited blue-purple fluorescence emission in methanol. At the same time, it is observed that in the presence of H₂O, there is a red shift in the maximum fluorescence emission peak of TAPB-DMTP-COF, which correlates with the H₂O content within a specific range. Notably, this redshift demonstrates a linear relationship with H₂O content from 4% to 80% in methanol. Our work presents novel insights for efficient analysis and detection of H₂O content in methanol and could be used for H₂O detection in other organic solvents.