Evaluation of Nitrogen-Based Polymeric Heterogeneous Catalysts for the Suzuki–Miyaura Cross-Coupling Reaction in Water

As environmental issues continuously increase, the development of effective and eco-friendly catalytic systems in organic chemistry is of great importance. To achieve this goal, two representative strategies are generally used: designing durable and efficient heterogeneous catalysts and using a clean and nontoxic solvent, such as water. Unfortunately, the interactions between widely used ligands and water have not been comprehensively investigated. Here, we first synthesized five similarly structured N-based palladium-embedded polymers, Pd@polyurea, Pd@polyurethane, Pd@polyimine, Pd@polyimide, and Pd@polythiourea, and then evaluated their performance and durability in organic reactions. The main aim of the study is to clarify the capabilities of N-based ligands in the Suzuki–Miyaura cross-coupling reaction under aqueous conditions by only changing the functional groups. To comprehensively evaluate the effects of the ligand functional groups, we used five criteria: (1) the structural stability, (2) the palladium loading, (3) the affinity with water, (4) the catalytic performance, and (5) the recyclability. We found that the catalytic performance and durability can be assessed and predicted using criteria 1–3. We believe that our strategy can provide a guide for designing efficient and eco-friendly heterogeneous catalytic systems.