Flow-Based

Covalent organic frameworks (COFs) constitute a class of functional porous materials with high stability and tunable porosity, rendering them attractive for adsorption-based applications. To study the interaction between COFs and target molecules, the quartz crystal microbalance with dissipation monitoring (QCM-D), which offers high sensitivity to mass changes with a sampling rate of ∼50 ms, is a well-suited tool for analyzing adsorption processes in real time. However, current QCM-D-based adsorption studies have remained largely qualitative, primarily relying on comparison of the magnitudes of frequency shifts. This occurs because the intrinsic mass of the film coated onto QCM-D sensors is often not determined, which prevents the quantification of the adsorption capacity. To address this challenge, a flow-based strategy to directly grow homogeneous COF thin films on sensor surfaces under QCM-D monitoring was established. This approach facilitates reliable mass determination, robust film attachment, and reproducible film preparation with precise control over film growth. To account for the contribution of the embedded solvent during film deposition, deuterated solvent exchange was performed. Through the use of methylene blue as a model adsorbate, liquid-phase QCM-D measurements revealed adsorption capacities of ∼31 mg·g