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[Display omitted] • PEI-functionalized cellulose foam (PEI-CF) with 3D network structure was prepared. • A fluorescence "on–off-on" appeared on the PEI-CF before and after Cr(VI) loaded. • The residual Cr(VI) concentrations in the effluent were below 0.05 mg/L. • Visual recognition of Cr(VI) on the PEI-CF was done in a wide pH range of 2–8. In this work, a novel PEI-functionized cellulose foam (PEI-CF) was prepared by crosslinking polyethyleneimine and cellulose with epichlorohydrin followed freeze drying. The resultant foam not only possessed a three-dimensional network structure but also emitted strong blue fluorescence. It can efficiently remove Cr(VI) from aqueous solution and reduce its concentration below 0.05 mg/L. Other competing anions including NO 3 −, Cl− and H 2 PO 4 − had no remarkable influence on Cr(VI) removal except SO 4 2−. Moreover, the PEI-CF demonstrated good regeneration performance. In addition, a reversible fluorescence "on–off-on" phenomenon was found for the PEI-CF before and after the Cr(VI) loaded under 365 nm UV light. By using the PEI-CF, the visual recognition of Cr(VI) was achieved in a wide pH range of 2–8 and low Cr(VI) concentration of 0.05 mg/L. Coexisting ions (Cu2+, Pb2+, Fe3+, Zn2+, Cr3+, SO 4 2−, Cl−, NO 3 −, H 2 PO 4 − and S2−) had no significant influence on the visual recognition of Cr(VI), exhibiting good selectivity. The PEI-CF showed great promise for the emergency monitoring and Cr(VI) removal in environmental water. [ABSTRACT FROM AUTHOR]