<p>Palladium (Pd) recovery from high-level liquid waste (HLLW) is essential both for meeting ever-growing industrial demands and for immobilizing radioactive waste through vitrification. However, developing robust and highly selective Pd adsorbents that can operate in strong acids remains a significant challenge. Herein, we report a novel cysteine-tailored 2D polyaramid (2DPA-Cys) that exhibits superior selectivity, high adsorption capacity, and remarkable reusability for Pd²⁺ in HNO₃ solutions. The abundant cysteine groups in 2DPA-Cys provide binding sites for selective Pd adsorption, whereas the 2D polyaramid core ensures chemical stability and allows peripheral functionalization. Adsorption studies using linear pseudo-second-order and Langmuir isotherm models indicate uniform single-layer chemisorption, with a maximum adsorption capacity of approximately 0.65 mmol/g in 0.5 M HNO₃. X-ray photoelectron spectroscopy (XPS) and density functional theory (DFT) analyses revealed that the strong and highly selective adsorption of Pd²⁺ by 2DPA-Cys is attributable to the formation of S-Pd-O coordinate bonds. This work highlights a design strategy that leverages 2DPA as a low-cost, acid-stable platform rich in coupling sites, demonstrating its potential for efficient Pd recovery in acidic environments and suggesting broader applications in nuclear waste management.</p>