"Rapid and sustainable methods for precious metal recovery are urgently needed to support circular economy initiatives. Herein, we introduce a one-pot mechanochemical route to synthesize a black phosphorus-polyglycerol (BP-PG) nanohybrid with enhanced interfacial reactivity for selective gold ion reduction. The process transforms inexpensive red phosphorus directly into amorphous BP and, subsequently, into BP-PG via planetary ball milling, thereby eliminating high temperatures, extended reaction times, and toxic solvents commonly used in conventional functionalized-BP nanomaterial syntheses. This ""grafting-from"" polymerization of glycidol onto BP yields a uniform, hydrophilic hybrid that can rapidly and selectively reduce gold ions to stabilized gold nanoparticles. Notably, BP-PG recovers more than three times its own weight in gold, far surpassing previously reported materials, while leveraging a scalable, cost-effective, and green production method. These findings underscore the critical role of synthetic strategy and material architecture in achieving high-performance nanohybrids, offering promising opportunities for precious metal recovery and broader interface-driven applications."