Architecting Multi‐Level Structures and Regulating Hydrophilicity of Covalent Organic Framework Aerogels for Optimizing Mass Transport Capacity

Abstract Architecting hierarchical structures in monolithic covalent organic frameworks (COFs) is vital for the applications of COFs in mass transport fields. The MXene‐coated bilayer aerogels containing β‐keto‐enamine COF (MX‐TpX‐COF) with different chain lengths of aromatic linkers are constructed for the study. The directional freezing method endowed the COF part and MXene coating with aligned channels, and the small pores mainly exist in the former, while the larger ones in the latter. The occurrence of multi‐level structures inside COF bulks, together with locally ordered vessels formed in the surfaces of MXene coating, are conducive to the mass transport of aerogels. Accordingly, the MX‐TpX‐COF aerogels showed attractive performance in oil/water separation and desalination, and even can be used for treating and desalinating oil‐contaminated seawater simultaneously. The mass transport rate and efficiency, however, strongly depended on the hydrophilicity and specific surface areas of COF bulks, which can be easily tuned by tailoring the chain lengths of aromatic linkers. This study offers a specific perspective on the utilization of bulk COF materials in marine governance, and also proposes a structural regulation way of multi‐functional integration for COF‐based aerogels.