Aminated metal-free red phosphorus nanosheets for adsorption and photocatalytic reduction of Cr(VI) from water

•RP-AP photocatalysts were prepared by a facile mechanical agitation method.•The introduction of –NH2 can effectively reduce Cr(VI) under visible-light.•RP-AP dramatically increased the electron-hole separation efficiency.•RP-AP exhibited a superior photocatalysis/adsorption synergy. The pollutant of hexavalent chromium (Cr(VI)) threats to the environment as well as to the human beings due to its strong toxicity, carcinogenicity, mobility and undegradability. Herein, a novel porous aminated red phosphorus (RP) nanosheet photocatalyst was synthesized to remove Cr(VI) from water through adsorption and in-situ photocatalytic reduction. The introduction of NH2 on the surface of RP nanosheet could effectively improve adsorption and photocatalytic reduction performance for Cr(VI) removal during visible light irradiation. As a result, the optimized RP-AP-0.5 (AP: 3-aminopropyltriethoxysilane) nanosheet displays the apparent reaction rate constant of 0.0190 min−1, which is 5.5 times higher than that of pure RP (0.0035 min−1), the 96.5% reduction efficiency for Cr(VI) within 120 min at pH = 4.8 ± 0.1 and still exhibits more than 95% removal efficiency after 5 cycles at the same condition. The enhanced Cr(VI) removal performance of the aminated RP nanosheet can be assigned to accelerating the interfacial reaction dynamics and more effective electron-hole separation owing to the presence of NH2 groups. This study provides a new method to develop high-efficiency metal-free photocatalysts with NH2 modification for Cr(VI) removal.