Magnetic photocatalysts with strong Rhodamine B (RhB) dye adsorption ability, i.e., tri-functional mesoporous composite γ-Fe₂O₃/α-Fe₂O₃/carbon aerogel (CA) structures, are successfully developed in this study. The removal capacity of RhB dyes of the as-prepared mesoporous structures is increased from 83.5% to 91% under visible light irradiation. The mesoporous structures can also be separated by an external magnetic field to avoid further separation steps, such as centrifugation. This work demonstrates that the as-prepared tri-functional mesoporous composite γ-Fe₂O₃/α-Fe₂O₃/CA structures have great potential in wastewater treatments.