This study developed phosphorus-doped boron nitride aerogel (P-BN) through a sol-gelmethod combined with low-dimensional boron nitride (BN) assembly, aiming to address the criticalchallenge of removing heavy metal ions in industrial wastewater. Structural characterization using X-ray photoelectron spectroscopy (XPS) and synchrotron X-ray absorption fine structure (XAFS)demonstrated that phosphorus doping introduced P—O—C and P—O functional groups, increased theinterlayer spacing of BN from 0.334 nm to 0.347 nm, and enhanced mesopore volume by 32.7%.Nitrogen adsorption-desorption isotherms further revealed a specific surface area of 465.4 m/g and anultralight bulk density of 0.80 mg/cm, significantly lower than that of the undoped BN (1.24mg/cm). Adsorption experiments conducted at 25 ℃ showed that P-BN exhibited a Cuadsorption capacity of 413.3 mg/g, outperforming BN by 14.4%, with maximum capacities forEnergy Environmental ProtectionZn, Cd, and Pb reaching 338.5, 253.9, and 234.8 mg/g, respectively. Kinetic analysis indicated thatthe adsorption process followed pseudo-second-order kinetics (R > 0.985) for P-BN, driven bychemisorption via coordination bonds between metal ions and PO groups, whereas BN adheredto pseudo-first-order kinetics (R > 0.996), indicative of physical adsorption. The Langmuir isothermmodels (R > 0.990) confirmed monolayer adsorption in both materials. Competitive adsorption tests inmixed solutions highlighted the selectivity of P-BN for Cu, with a selectivity coefficient α(Cu/Pb)of 2.17, which was attributed to d-orbital electron interactions between Cu and P—O groups.Thermodynamic studies identified 25 ℃ as the optimal temperature, beyond which the adsorptioncapacity decreased due to accelerated desorption kinetics. The superior adsorption performance of P-BN was attributed to three synergistic effects: (1) phosphorus-induced active sites acceleratingsurface reactions, (2) optimized mesoporous structure (average pore size reduced to 2.9 nm from 3.4 nmin BN) enhancing ion diffusion, and (3) stabilized coordination environments via P—O bonding.Furthermore, the scalable synthesis using low-toxicity precursors (boric acid, melamine, and redphosphorus) and the ultralight density of the material <1 mg/cm enable cost-effective fabrication andintegration into dynamic filtration systems for large-scale wastewater treatment. Future research willfocus on pilot-scale validation of long-term stability and mechanistic studies to elucidate the selectiveadsorption pathways in complex multi-ion environments.