Polydopamine-stabilized Cu₂O/ZnO nanocomposites for sustainable photocatalytic reduction of maleic acid in water

The photocatalytic reduction of maleic acid (MA) to succinic acid (SA)1 represents a valuable transformation in green chemistry2, as SA is a key platform chemical and a potential intermediate in greener alternative pathways toward nylon production. This study presents the synthesis, characterization and application as catalyst of a new Cu₂O/ZnO nanocomposite encapsulated in a polydopamine (PDA) shell, which plays a crucial role (thanks to its redox active properties) in overcoming the typical photodegradation of copper oxide under UV irradiation3. The catalyst was synthesized via a fast, eco-friendly, sonochemical route in water and tested in the photoreduction of MA under 254 nm UV light in water. When combined with a catalytic amount of sodium ascorbate, the system achieved up to 61% yield and 67% selectivity in SA over 72 h. PDA enhances catalyst durability and charge separation, while isotopic experiments confirmed that water—not ascorbate—is the hydrogen source, supporting a radical-mediated mechanism. The use of ZnO as a safer alternative to TiO₂, coupled with PDA's biocompatibility and the use of ascorbate as a green co-catalyst, demonstrates the potential of this system as a scalable, environmentally friendly route for value-added chemical production.

References
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