Enhanced Depolymerization of Poly(Bisphenol A Carbonate) via Robust Mesoporous CaCO₃/CaTiO₃ Nanocomposites Featuring Synergistic Acid–Base Sites and Oxygen Vacancies

Abstract

Poly(bisphenol A carbonate) (BPA-PC) exhibits high resistance to natural degradation and releases hazardous bisphenol A (BPA), raising significant environmental and health concerns. Chemical recycling through alcoholysis represents a promising strategy to address this issue, however, currently available catalytic systems are hampered by several drawbacks including undesirable side reactions, poor recyclability, low catalytic activity, and complex preparation processes. Herein, we report a robust mesoporous CaCO₃/CaTiO₃ composite catalyst (CTO) fabricated via a facile sol-gel method coupled with controlled calcination, engineered to address these challenges through synergistic acid-base sites and oxygen vacancies (OVs). Calcination at 500 °C for 5 h (CTO-500-5) constructed a biphasic composite with well-defined mesoporosity, balanced Lewis acid and basic sites, and abundant OVs, enabling efficient alcoholysis of BPA-PC under batch and flow conditions. For batch reaction, the catalyst demonstrated broad applicability, efficiently depolymerizing diverse commercial BPA-PC products into BPA with yields of 80–91%, while also adapting to multiple nucleophilic alcohols to generate high-value carbonates. It retained full activity across 10 reuse cycles with no discernible deactivation. For scalable recycling, the catalyst was immobilized in a fixed-bed flow reactor. This setup enabled continuous methanolysis and glycolysis with 100% BPA selectivity and stable operation for over 30 h and 40 h, respectively. Simultaneously, the catalytic activity was readily recovered via alkali treatment regeneration. This work demonstrates that the CaCO₃/CaTiO₃ catalyst, with its tunable structure, acid-base synergy, and excellent stability, provides a sustainable and industrially viable strategy for closed-loop chemical recycling of BPA-PC.