*Article* **Metal-Organic Frameworks Decorated Cu2O Heterogeneous Catalysts for Selective Oxidation of Styrene**

**Mengyi Han 1,2,†, Xue Tang 1,2,†, Peng Wang 1,2, Zhiyong Zhao 1,2, Xiaohua Ba <sup>1</sup> , Yu Jiang <sup>1</sup> and Xiaowei Zhang 1,\***


† These authors contributed equally to this work.

**Abstract:** The selective oxidation of styrene with highly efficient, environmentally benign, and costeffective catalysts are of great importance for sustainable chemical processes. Here, we develop an in situ self-assembly strategy to decorate Cu-based metal-organic framework (MOF) Cu-BDC-NH<sup>2</sup> nanocrystals on Cu2O octahedra to construct a series of Cu2O@Cu-BDC-NH<sup>2</sup> catalysts for selective oxidation of styrene. Using H2O<sup>2</sup> as green oxidants, the optimized sample of Cu2O@Cu-BDC-NH<sup>2</sup> -8h could achieve 85% styrene conversion with 76% selectivity of benzaldehyde under a mild condition of 40 ◦C. The high performance of the as-prepared heterogeneous catalysts was attributed to the well-designed Cu+/Cu2+ interface between Cu2O and Cu-BDC-NH<sup>2</sup> as well as the porous MOF shells composed of the uniformly dispersed Cu-BDC-NH<sup>2</sup> nanocrystals. The alkaline properties of Cu2O and the –NH<sup>2</sup> modification of MOFs enable the reaction to be carried out in a base-free condition, which simplifies the separation process and makes the catalytic system more environmentally friendly. Besides the Cu2O octahedra (od-Cu2O), the Cu2O cuboctahedrons (cod-Cu2O) were synthesized by adjusting the added polyvinyl pyrrolidone, and the obtained cod-Cu2O@Cu-BDC-NH<sup>2</sup> composite also showed good catalytic performance. This work provides a useful strategy for developing highly efficient and environmentally benign heterogeneous catalysts for the selective oxidation of styrene.

**Keywords:** metal-organic frameworks; Cu2O; styrene oxidation; H2O<sup>2</sup> ; base free
