Turning Waste into Wealth: Remotely NIR Light‐Controlled Precious Metal Recovery by Covalently Functionalized Black Phosphorus.

It is a great challenge to refine precious metals from e‐wastes under mild conditions without hazardous reagents. Herein, black phosphorus (BP) was covalently functionalized with poly(N‐isopropylacrylamide) (PNIPAM) to obtain thermo/near‐infrared (NIR)‐responsive BP−P for precious metal recovery. Precious metals (Au, Ag, and Pd) with higher redox potentials than BP−P could be efficiently recovered by reduction‐driven enrichment. Taking Au as an example, the recovery process presented fast kinetics (<15 min), excellent selectivity, and high efficiency (≈98 %). Remote operation with NIR light could generate heat by BP, which induced the hydrophilic‐to‐hydrophobic transition of PNIPAM, allowing the spontaneous gathering, facile collection, and practical recycle of BP−P following Au extraction. Thanks to the unique features of BP−P, not only could high‐quality Au nanoparticles (20–30 nm) be economically extracted (cost: $0.731–1.222 g−1 Au nanoparticles; 5–6 orders of magnitude lower than the market price), but also the formed BP−P‐Au nanocomposites have potential application in hydrogen evolution reaction. [ABSTRACT FROM AUTHOR]