The utilization of solar evaporator for interfacial seawater evaporation and wastewater treatment presents a promising concept; however, inadequate evaporation and degradation rates and complicated preparation procedures significantly hinder its practical application. Herein, the black g-C3N4/loofah/chitosan (BCN/LF/CS) hydrogel as an efficient dual-function solar evaporator was constructed for desalination coupled with antibiotic degradation. The experimental results show that in 3.5 wt% NaCl solution, the effective evaporation rate of optimal BCN-1/LF/CS evaporator can reach 2.1 kg m−2 h−1, and maintaining 91.4 % degradation of tetracycline (TC) solution (50 mg/L) within 6 h irradiation. This work introduced here combines the advantages of photothermal evaporation and photocatalytic degradation to obtain fresh water from a complicated water environment, providing inspiration for future exploration of photocatalyst construction and extensive application in wastewater purification.