<p>Despite its wide applicability, the synthesis of α-Al₂O₃ with nanoscale dimensions and a well-developed porous structure continues to be a formidable challenge. This study reports the synthesis of a versatile 2-dimensional (2D) α-Al₂O₃ nanomaterial using a simple solution combustion method. The 2D α-Al₂O₃ nanomaterial calcined at 550 °C (denoted as α-Al₂O₃ 550) exhibited unique characteristics, including a hierarchical porous structure (5–30 nm), nanosheet morphology (length: 2.81–4.97 μm, width: 0.78–0.97 μm, and thickness: 4.7–9.8 nm), surface-engineered grain boundaries, BET surface area of 56 m²/g, and optimum amount of acid sites, as confirmed by SEM, TEM, AFM, and NH₃-TPD analyses. The 2D α-Al₂O₃ 550 nanosheet catalyst showed excellent activity in upcycling post-consumer PET plastic bottles into a valuable monomer, bis(2-aminoethyl) terephthalamide (BAET), using ethylenediamine as both the reactant and solvent. An impressive 92% isolated yield of BAET was achieved over the 2D α-Al₂O₃ 550 nanosheet catalyst, outperforming several metal oxides, such as γ-Al₂O₃, Nb₂O₅, CeO₂, and MnO_x. The α-Al₂O₃ 550 catalyst is highly stable and exhibits good reusability over five consecutive cycles, with only a slight decrease in BAET yield from 92% in the first cycle to 85% in the fifth cycle. The process is scalable (5 g), efficiently employed for upcycling various post-consumer PET bottles with yields of 90%, and meets green chemistry metrics. This study highlights 2D α-Al₂O₃ 550 nanomaterial as a robust, economically viable catalyst, offering a practical route for the upcycling of plastic waste.</p>