Utilizing Recycled Expanded Polystyrene Plastics to Stabilize Metal–Organic Frameworks for Heterogeneous Catalysis

Abstract

Polystyrene plastics present significant environmental and human health threats due to their poor recyclability and degradability. However, leveraging their properties to enhance material performance stands out as one of the most effective strategies for mitigating these issues. Here, we have employed recycled expanded polystyrene plastics to manufacture metal–organic framework/expanded polystyrene plastic composites (MOF@EPP) using an adverse solvent precipitation method. This method simultaneously recycles EPPs and safeguards moisture-sensitive MOFs. Due to the exceptional hydrophobic properties of EPPs, HKUST−1@EPP can maintain structural integrity even when immersed in water for 30 days. This method is applicable to other moisture-sensitive MOFs, such as MOF−74(Zn) and MIL−53(Al). The HKUST−1@EPP composite also exhibits desirable heterogeneous catalytic activity in the Knoevenagel condensation reaction between benzaldehyde and acrylonitrile. The conversion rate can reach 94.9% within 4 h at 90 °C and does not exhibit a significant decrease even after six cycles, even in the presence of water. This study not only introduces a novel concept for recycling polystyrene plastics, but also offers a practical strategy for safeguarding moisture-sensitive MOFs.