Interface-Engineered Electron-Deficient Nickel Species for Efficient Depolymerization of Polyethylene Terephthalate

Polyethylene terephthalate (PET) is the most abundant polyester plastic. Its chemical recycling mainly relies on homogeneous catalysis, often suffering from difficult catalyst separation and substantial waste generation. Previous work using heterogeneous catalysts has primarily focused on increasing Lewis acidity through variation of metal oxide types to improve performance, but catalyst activity remains limited. Here, we adopt an alternative strategy for modulating Lewis acidity with enhanced control by systematically tuning electronic properties of structurally versatile Ni active sites. Nickel can readily form intermetallics and layered double hydroxide (LDH) derivatives, providing substantial flexibility for modulating its electronic structure. We establish an electron-deficiency-dependent activity framework and discover a Ni₃Ga/NiAlO_x catalyst that exhibits unexpectedly high activity, surpassing more strongly Lewis-acidic fully oxidized Ni species and delivering an order-of-magnitude activity enhancement compared with conventional Lewis-acidic oxides. This high activity originates from electron-deficient interfacial Ni sites where electron withdrawal from O in LDH-derived NiAlO_x and electron donation from Ga in intermetallic Ni₃Ga result in appropriate Lewis acidity, enabling near-quantitative dimethyl terephthalate recovery from post-consumer PET. Theoretical and experimental validation suggests that such bidirectional electronic modulation balances substrate activation and product desorption, thereby maximizing catalytic efficiency. The catalyst is prepared via an industrially-established co-precipitation method and is readily scalable.