A π-Conjugated Covalent Organic Framework Enables Interlocked Nickel/Photoredox Catalysis for Light-Harvesting Cross-Coupling Reactions

Abstract

Covalent organic frameworks (COF) is an outstanding manifesto for heterogeneous photocatalysis. Herein, we synthesized a pyrene-based two-dimensional C=C linked π-conjugated COF via Knoevenagel condensation and anchored Ni(II)-center through bipyridine moieties. Instead of traditional dual metallaphotoredox catalysis, the mono-metal decorated Ni@Bpy-sp2C-COF interlocked the catalysis mediated by light and the transition metal. Under light irradiation, enhanced energy and electron transfer in the COF backbone, as delineated by the photoluminescence, electrochemical, and control experiments, expedited the excitation of Ni centers to efficiently catalyzes diverse photocatalytic C–X (X = B, C, N, O, P, S) cross-coupling reactions with efficiencies orders of magnitude higher than its homogeneous controls. The COF catalyst tolerated a diverse range of coupling partners having various steric and electronic properties under these conditions delivering the products with up to 99% yields. A large number of functional groups were also accommodated for the model reaction. Some reactions were performed on a gram scale and were applied to diversify pharmaceuticals and complex molecules to demonstrate the synthetic utility. The Ni@Bpy-sp2C-COF catalyst could be recovered and reused for several cycles without significant loss in catalytic activities.

Incorporation of Ir(C^N)2(N^N)-NiCl2 in a (N^N)-covalent organic framework for transcendent dual catalysis in photochemical cross-coupling synthesis

“…34 For instance, their valence band, conduction band, and band gap can be tuned to be within the visible light range. 35 Additionally, COFs can be easily modied with metal catalysts to create dualcatalysis systems, [36][37][38] with the simultaneous anchoring of photosensitizers and metal catalysts leading to signicantly enhanced photocatalytic performance.…”