Programmable Photocatalytic Activity of Multicomponent Covalent Organic Frameworks Used as Metallaphotocatalysts

Abstract

The multicomponent approach allows to incorporate several functionalities into a single covalent organic framework (COF) and consequently allows the construction of bifunctional materials for cooperative catalysis. The well‐defined structure of such multicomponent COFs is furthermore ideally suited for structure‐activity relationship studies. We report a series of multicomponent COFs that contain acridine‐ and 2,2’‐bipyridine linkers connected through 1,3,5‐benzenetrialdehyde derivatives. The acridine motif is responsible for broad light absorption, while the bipyridine unit enables complexation of nickel catalysts. These features enable the usage of the framework materials as catalysts for light‐mediated carbon−heteroatom cross‐couplings. Variation of the node units shows that the catalytic activity correlates to the keto‐enamine tautomer isomerism. This allows switching between high charge‐carrier mobility and persistent, localized charge‐separated species depending on the nodes, a tool to tailor the materials for specific reactions. Moreover, nickel‐loaded COFs are recyclable and catalyze cross‐couplings even using red light irradiation.

Nickel Metallaphotoredox Buchwald–Hartwig Amination Reactions: A Perspective on Irradiation Light Wavelength

“…Recently, the same group further developed a series of multicomponent COFs to deepen the study of structure-activity relationship using light-mediated carbon-heteroatom (CÀ N and CÀ S, Scheme 13b) bonds formation. [59] These COFs contained 1,3,5-benzenetrialdehyde derivatives as connected nodes, Bpy unit as binding sites of nickel catalysts, and Acr responding for broad light absorption. Detailed evaluation unveiled that the catalytic activity was correlated to the keto-enamine tautomerization, which enabled switching between high charge-carrier mobility and persistent localized charge-separated species according to different nodes.…”

“…Recently, the same group further developed a series of multicomponent COFs to deepen the study of structure‐activity relationship using light‐mediated carbon‐heteroatom (C−N and C−S, Scheme 13b) bonds formation [59] . These COFs contained 1,3,5‐benzenetrialdehyde derivatives as connected nodes, Bpy unit as binding sites of nickel catalysts, and Acr responding for broad light absorption.…”

Low band gap semiconducting covalent organic framework films with enhanced photocatalytic hydrogen evolution

“…21 Besides the choice of such building blocks, the way how they are connected also plays a crucial role in allowing intramolecular charge transfer and electronic communication between the p-conjugated building blocks. 22,23 Numerous COFs have been employed so far in combination with co-catalysts and sacricial electron donors (SEDs) to achieve photocatalytic HER. 20 The photocatalytic performance of a COF depends on several factors, primarily, its light absorption ability (i.e., band gap) and band position, the ability of charge separation and transport, along with crystallinity, porosity, stacking, stability, morphology, water dispersibility, pH and co-catalyst.…”

Solar Light Driven H2O2 Production and Selective Oxidations Using a Covalent Organic Framework Photocatalyst Prepared by a Multicomponent Reaction

“…Beside hydrogen and hydrogen peroxide production, COFs have also been applied as photocatalysts for organic transformation reactions [51–56] . To synthesize diverse fine chemicals, selective oxidation of both aliphatic and aromatic compounds are elemental reactions.…”

“…Beside hydrogen and hydrogen peroxide production, COFs have also been applied as photocatalysts for organic transformation reactions. [51][52][53][54][55][56] To synthesize diverse fine chemicals, selective oxidation of both aliphatic and aromatic compounds are elemental reactions. The conventional oxidation processes carried out industrially employ harsh conditions and hazardous oxidants, yielding production of waste byproducts and increased operational cost with drastic impact on the environment.…”