Abstract
The strong coordination between metal ions and binding moieties in functional porous materials is central to the design and advancement of heterogeneous catalysis. In this study, we have successfully immobilized catalytically active iridium ions on a two-dimensional covalent organic framework (COF) having bipyridine moieties using a programmed synthetic procedure. The iridium immobilized framework, Ircod(I)@Py-2,2′-BPyPh COF, had high porosity, good stability, and exhibited excellent catalytic activity for C—H borylation, as compared with the pristine framework. Additionally, Ircod(I)@Py-2,2′-BPyPh COF was found to be an efficient catalyst for a series of electronically and sterically substituted substrates. The immobilized COF possessed excellent reusability, recyclability, and retention of crystallinity. This report highlights the role of porous materials as an ideal decorating platform for conducting a wide range of potent chemical conversions.
Highlights
Catalytic transformation of C−−H bonds is extremely challenging, and an unambiguous understanding of the strategies to activate this bond is central to numerous organic transformations.1–20 Over the past years, there has been extraordinary progress in the development of homogeneous transition metal catalysts for C−−H functionalization including oxygenation,3 borylation,21–24 carbonylation,25 and dehydrogenation.26 Ir,27,28 Rh,29–31 Re,32 and Ru33,34 based catalysts have been extensively used for C−−H borylation of hydrocarbon using bis(pinacolato)diboron (B2Pin2) as the borylating agent
To address the drawbacks of homogeneous catalytic systems such as their lack of recyclability and reusability and the involvement of expensive metals, extraordinary effort has been made by researchers in recent years, and this has led to the development of Ir-based heterogeneous catalysts for C−−H borylation
We demonstrate the immobilization of an Ir-complex on a bipyridine-based covalent organic framework (COF), Ircod(I)@s Py-2,2′-BPyPh COF, which is a promising and efficacious heterogeneous catalyst for C−−H borylation with excellent recyclability, reusability, and retention of crystallinity
Summary
Catalytic transformation of C−−H bonds is extremely challenging, and an unambiguous understanding of the strategies to activate this bond is central to numerous organic transformations. Over the past years, there has been extraordinary progress in the development of homogeneous transition metal catalysts for C−−H functionalization including oxygenation, borylation, carbonylation, and dehydrogenation. Ir,27,28 Rh, Re,32 and Ru33,34 based catalysts have been extensively used for C−−H borylation of hydrocarbon using bis(pinacolato)diboron (B2Pin2) as the borylating agent. Rh,29–31 Re, and Ru33,34 based catalysts have been extensively used for C−−H borylation of hydrocarbon using bis(pinacolato)diboron (B2Pin2) as the borylating agent These studies have emphasized that transition metal-catalyzed C−−H borylation of aromatic compounds is an effective, efficient, and reliable strategy for the synthesis of organoboron compounds. To address the drawbacks of homogeneous catalytic systems such as their lack of recyclability and reusability and the involvement of expensive metals, extraordinary effort has been made by researchers in recent years, and this has led to the development of Ir-based heterogeneous catalysts for C−−H borylation.. Scitation.org/journal/apm heterogeneous platforms including mesoporous silica, metalorganic frameworks (MOFs), organosilica-nanotubes, and covalent triazine frameworks have been reported. These wellestablished Ir-based materials exhibit high catalytic activity and selectivity for C−−H borylation of arenes. Yaghi et al employed a porphyrin monomer to construct porphyrin-based COFs for the electrocatalytic CO2 reduction, and Cui’s group synthesized BINOL-based COFs to catalyze the asymmetric addition reaction of diethylzinc to aldehydes. In addition, Banerjee et al reported that β-ketoenamine linked COFs and porphyrin embellish frameworks were effective organocatalysts for cascade reactions. Marinescu and co-workers reported Re(I) bipyridine scaffold to synthesize COFs for CO2 reduction, while our group, in collaboration with Chen and Zhang’s research group, recently reported the use of squaramide-decorated COF for organocatalysis. we demonstrate the immobilization of an Ir-complex on a bipyridine-based COF, Ircod(I)@s Py-2,2′-BPyPh COF, which is a promising and efficacious heterogeneous catalyst for C−−H borylation with excellent recyclability, reusability, and retention of crystallinity
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