β-Diketimine appended periodic mesoporous organosilica as a scaffold for immobilization of palladium acetate: An efficient green catalyst for Wacker type reaction

• Synthesis of novel periodic mesoporous organosilica (PMO) with β-diketimine centers.
• β-Diketimine centers in PMO serve as an scaffold for coordination with Pd(OAc)2.
• Pd2+ incorporated PMO offers a molecular distribution of Pd at +2 state.
• Pd2+ incorporated PMO shows selective oxidation of styrene to acetophenone.
• PMO catalyst presents good catalytic conversion, selectivity, and recyclability.

A series of β-diketimine appended periodic mesoporous organosilicas (PMOs) were prepared and characterized. These PMOs were found to be an excellent scaffold for the immobilization of palladium acetate [Pd(OAc)2] through the complexation between Pd(OAc)2 and iminic nitrogen atoms of β-diketiminate, leading to the formation of efficient heterogeneous catalysts (Pd/PMOs) for the oxidation of styrene. Catalytic evaluations show that, in liquid phase using H2O2 as oxidant, Pd/PMOs could promote styrene to undergo Wacker type reaction with a high selectivity of up to 100% toward the formation of acetophenone, a useful chemical with high demand in the global market. The novel solid catalyst offers a good catalytic recyclability with consistently high catalytic activity. In addition, it was experimentally demonstrated that H2O2 plays an important role to prevent unwanted catalyst deactivation. Thus, the current work presents a convenient approach for the direct production of acetophenone from styrene.

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