Acridine‐Functionalized Covalent Organic Frameworks (COFs) as Photocatalysts for Metallaphotocatalytic C−N Cross‐Coupling

Abstract

Covalent organic frameworks (COFs) are structurally tuneable, porous and crystalline polymers constructed through the covalent attachment of small organic building blocks as elementary units. Using the myriad of such building blocks, a broad spectrum of functionalities has been applied for COF syntheses for broad applications, including heterogeneous catalysis. Herein, we report the synthesis of a new family of porous and crystalline COFs using a novel acridine linker and benzene-1,3,5-tricarbaldehyde derivatives bearing a variable number of hydroxy groups. With the broad absorption in the visible light region, the COFs were applied as photocatalysts in metallaphotocatalytic CÀ N cross-coupling. The fully β-ketoenamine linked COF showed the highest activity, due to the increased charge separation upon irradiation. The COF showed good to excellent yields for several aryl bromides, good recyclability and even catalyzed the organic transformation in presence of green light as energy source.

One-Pot Cascade Construction of Nonsubstituted Quinoline-Bridged Covalent Organic Frameworks

“…1d. the imine carbon peak in 13 C-labeled NQ-COF A1 -OPR at 157 ppm disappears completely while there newly appears a new peak at 155 ppm for the quinoline carbon of 13 C-labeled NQ-COF A1 -OPR. The formation of the quinoline-linked COF was further supported by high-resolution X-ray photoelectron spectroscopy (XPS) analysis as the binding energy of N 1s in C = N fragments shifts from ~ 398.9 eV to the higher 399.2 eV in terms of N 1s peak (Supplementary Fig.…”

“…On the other hand, there still obvious residue of C = N bonds for NQ-COF A1 without MgSO 4 addition, supporting that OPR can only smoothly operated in the presence of MgSO 4 . Subsequently, isotopically enriched 13 C-labeled aldehyde was synthesized. After the structure was veri ed by FT-IR spectra (Supplementary Fig.…”

“…After the structure was veri ed by FT-IR spectra (Supplementary Fig. 3), the 13 C-labeled COF A1 and NQ-COF A1 -OPR were afforded in the same condition for collecting the solid-state 13 C crosspolarization magic angle rotation (CP-MAS) NMR spectra. As shown in Fig.…”

“…[1][2][3] With periodic structure, high accessible surface area, well-de ned porosity, and designable construction, COFs are burgeoning as a new research frontier in energy storage, 4,5 separation, 6,7 sensing, 8-10 and catalysis. [11][12][13][14][15] It is well recognized that the reversibility of covalent linkage serves as the major driving force for formation of long-range ordered COFs. This dynamic nature of bonds, however, poses a negative impact to the chemical stability of COFs, thus giving rise to an unavoidable trade-off between crystalline and robustness.…”

Antiaromatic Covalent Organic Frameworks Based on Dibenzopentalenes

“…This class of well-defined porous materials can serve as a platform to translate the properties of molecules to bulk insoluble materials. The combination of a high surface area, accessible pores, and efficient electronic delocalization makes COFs ideal candidates for applications in energy storage, [41][42][43] as well as gas storage and separation, 44,45 (photo)catalysis, [46][47][48][49] and optoelectronics. [50][51][52][53][54][55][56][57][58] Analogous to crystalline COFs, amorphous porous organic polymers (POPs) are constructed of functional monomers.…”