Tandem Oxidation-Condensation Tandem Catalysis via a Multifunctional Cu-Based Metal-Organic Framework.

Abstract

The development of heterogeneous catalysts for tandem reactions remains a significant challenge for practical applications, primarily due to the need for multiple isolated catalytic sites. This study presents a novel metal-organic framework (MOF), Cu-AIPA, formulated as Cu(AIPA)(DMF)2 (AIPA: 2-amino isophthalic acid, DMF: N, N-dimethylformamide). The Cu-AIPA framework integrates three distinct catalytic mechanisms: redox activity, Brønsted basicity, and Lewis acidity. The structure of Cu-AIPA features redox-active Cu(II) centers and Brønsted basic sites, enabling the sequential transformation of alcohols to aldehydes and their subsequent condensation into imines. The close spatial arrangement of these redox-active/Lewis acidic and basic sites within the confined pores of Cu-AIPA facilitates efficient tandem catalysis. This process involves oxidizing benzyl alcohol to benzaldehyde using TEMPO without requiring an external base, followed by amine condensation. Compared with HKUST-1, another Cu-based MOF with a high surface area, Cu-AIPA demonstrated superior catalytic performance at room temperature. Recyclability tests revealed that Cu-AIPA retained over 90% conversion efficiency across at least three catalytic cycles. This study highlights the potential of MOFs incorporating multiple catalytic sites and confined pore structures for tandem reactions, emphasizing their potential for scalable and sustainable industrial applications.