Multiscale Covalent Organic Framework (COF) Films for Task-Specific Sensing in Multicomponent Gases

Gas sensing is vital for ecological protection in agriculture, early disease diagnosis in biomedicine, and safety in industrial production. Covalent organic frameworks (COFs), a new class of porous polymer materials, can be customized through specific ligand selection to tailor pore sizes and active sites, enabling them to selectively enrich and interact with targeted gas molecules, making them promising candidates for gas sensing. To advance their use in this field, it is essential to investigate the mechanisms of the complex interactions between COFs and target molecules as well as to improve COF film fabrication methods. This review outlines design strategies for COF films across multiscale: molecular interaction mechanisms, macroscopic interfacial synthesis methods, and microscale/nanoscale approaches such as double-layer films for filtration and micro/nanostructured films for improved gas transfer. Finally, several key research directions are proposed to improve the suitability of COF-based materials for gas sensing in complex environments.