Synthesis, characterization and catalytic performance of palladium supported on pyridine‐based covalent organic polymer for Suzuki‐Miyaura reaction

Abstract

A bipyridine‐based covalent organic polymer (COP) was successfully synthesized by condensation of trimesoyl chloride (TMC) and 2,2′‐bipyridine‐5,5′‐diamine (Bpy) under ambient conditions. This material was modified by coordination of PdCl2 to COP framework, affording a hybrid material, Pd@TMC‐Bpy COP, which was applied as a highly efficient heterogeneous catalyst for Suzuki‐Miyaura reaction under ligand‐free conditions in ethyl lactate. The catalyst could be reused for five times without obvious loss of its activity.

Control over Charge Separation by Imine Structural Isomerization in Covalent Organic Frameworks with Implications on CO2 Photoreduction

“…Thomas and co-workers dove deeper into the impact of imine reversal reporting changes in the absorption, band alignment, photoconductivity, and photocatalytic behavior, but the fundamentals for why imine reversal changes these properties remain elusive. A related trend in COF literature is the use of 5,5′-dicarbaldehyde-2,2′-bipyridine (CHO-bpy) as an MC docking site for the formation of photocatalytic COF structures with a variety of comonomers. − The structural diversity of comonomers with 5,5′-diamino-2,2′-bipyridine (NH 2 -bpy), however, is sparse. − When NH 2 -bpy does appear in the literature it is typically stabilized by hydrogen bonding interactions from 1,3,5-triformylphloroglucinol that undergoes keto–enol tautomerization to transform the imine bond into an amine and only a few references exist that polymerize NH 2 -bpy without additional hydrogen bonding stabilization. , Of these, the structures either make use of a tetratopic pyrene monomer that has been shown to be a beneficial crystallization agent, or the crystallinity and porosity of the sample are low . These inherent structural challenges in imine structural isomerism should be recognized as fundamentally important to understand the dynamics of COF formation, and discovering the electronic effects of imine reversal is important to understand how such a ubiquitous linker may affect the performance in COF photocatalysts.…”

Confining Palladium Nanoparticles in Microporous Tetrastyrene Polymer Enables Efficient Size-Selective Heterogeneous Catalysis

“…During the past decades, noble metal nanoparticles (NPs) have attracted a broad concern in theoretical study and practical application by virtue of their excellent catalytic activity. − Especially, palladium (Pd) nanoparticles (NPs) have been applied as crucial catalysts to many chemical transformations. − Compared to bulk form, superfine Pd NPs show many advantages, such as large surface area and high chemical activity as well as unique interaction specificity, and thus exhibit remarkably enhanced catalytic activity. − However, it is hard to control the size distribution of Pd NPs during the synthetic process on account of their preferential tendency to aggregate to form large particles . To solve this problem, numerous efforts have been made on the development of porous carriers to control the size of Pd NPs, such as zeolites, − mesoporous silicon, − metal–organic frameworks (MOFs), − and covalent organic frameworks (COFs). − It is well-known that the size distribution of noble metals in a porous carrier depends on the microstructure of the carrier . Therefore, the exploration and development of a novel carrier with tunable micropore to control the size of Pd NPs are highly desirable.…”

Continuous Ligand-Free Suzuki–Miyaura Cross-Coupling Reactions in a Cartridge Flow Reactor Using a Gel-Supported Catalyst

“…Heterogeneous systems have progressed from materials such as Pd/C and graphene/graphite oxides to dense supports (e.g., silica and magnetic particles). Further work has included bulk supports, including metal–organic frameworks (MOFs), covalent–organic frameworks (COFs), and polymer networks (e.g., poly NIPAM, , cyclodextrin, , and polysiloxanes). , A significant amount of research has focused on understanding the role of the Pd species in heterogeneous catalysts and the mechanism by which they proceed. , The heterogeneous catalysis approach does not require catalyst recovery but has notoriously lower reproducibility, accessibility, and selectivity compared to homogeneous catalysis. − These drawbacks of continuous-flow organic synthesis necessitate developing alternative catalytic flow reactors with higher flexibility, modularity, and robustness.…”

“…Heterogeneous systems have progressed from materials such as Pd/C 17 and graphene/graphite oxides 18 to dense supports (e.g., silica 19 and magnetic 20 particles). Further work has included bulk supports, including metal−organic frameworks (MOFs), 21 covalent−organic frameworks (COFs), 22 and polymer networks 23 (e.g., poly NIPAM, 7,24 cyclodextrin, 25,26 and polysiloxanes). in heterogeneous catalysts and the mechanism by which they proceed.…”