NHC-Cu(I)Br Encapsulated UiO-67 Metal-Organic Framework and Its Application in Heterogeneous Catalysis

Abstract

The transition metal complexes of N-heterocyclic carbenes (NHCs), especially, ligated copper (I) NHC complexes, have been widely utilized in various catalytic reactions, such as C-B, C- C, and C-N coupling reactions. However, the reuse and recycling of these complexes remains a challenge. On the other hand, the Metal-Organic Frameworks (MOFs) have been recognized as promising heterogeneous catalysts due to their hybrid polymeric structure that combines inorganic and organic components. To address this challenge, we have developed NHC-coordinated CuBr (NHC = Bn2Im; 1,3-dibenzyl-imidazol-2-ylidene) complex was encapsulated in UiO-67 MOF, ((Bn2Im)2CuBr@UiO-67), and utilized it for several organic transformations. The reusability and structural integrity of this heterogeneous catalyst were verified through various characterization techniques, which include PXRD, ATIR, FESEM, HRTEM, XPS, etc. This NHC-coordinated CuBr complex was encapsulated in UiO-67 MOF, ((Bn2Im)2CuBr@UiO-67) and further utilized toward the regioselective protoboration of terminal alkynes. Furthermore, we have explored this heterogeneous catalyst (Bn2Im)2CuBr@UiO-67 for the three-component coupling reactions, such as A 3 and KA 2 coupling, resulting in the synthesis of propargyl amine in excellent yields. We also studied the recyclability of the catalyst for this reaction, which was found to be up to five cycles.