Covalent organic frameworks (COFs), have been used as potential photocatalysts for the degradation of antibiotics, but their poor recyclability limits the application in practical environment. In this paper, a novel melamine sponge@COF composite sponge was successfully prepared via a one-pot method by “reactive seeding” strategy. Such strategy enables the uniform and sturdy growth of small-sized COF-TpTt on the melamine sponge (MS) fibers. The composite sponge (MS@TpTt) effectively overcomes the difficulty of recycling for the powder character of general COFs, and shows excellent photocatalytic activity towards the degradation of tetracycline antibiotics under visible light. The finding in this work provides a simple strategy for the preparation of COF-based composite monolithic materials with high degradation performance, easy circulation and high stability for desired catalytic applications.