Development of Porous Cobalt-/Copper-Doped Carbon Nanohybrids Derived from Functionalized MOFs as Efficient Catalysts for the Ullmann Cross-Coupling Reaction: Insights into the Active Centers

Newly emerging poly-functional
metal–organic frameworks
(MOFs) have been proved to be a promising alternative method for the
hard/soft template to generate different carbon-based heterostructures.
Herein, we have synthesized a sulfonyl-amide-based MOF (TMU-81) with
an exceptionally high concentration of functional groups, which can
interact strongly with metal ions and utilized it as a double-template
platform to fabricate versatile catalysts by remaining structural
regularity. The preloaded copper ions resided in pores of TMU-81 not
only play a significant role in pore-forming by in situ renovating
into Cu nanoparticles via the pyrolysis process but also trigger the
morphological transformations of the resultant metal/carbon hybrids.
The morphology of the TMU-81 was tuned from truncated octahedron to
cubic in cobalt-/copper-doped carbon nanohybrids (MC-81), and also
the Brunauer–Emmett–Teller surface area increased significantly
up to 1450 cm2/g. Benchmarks have been established for
the performance of TMU-81, pyrolyzed TMU-81 (P-TMU-81), and MC-81s,
as efficient and robust catalysts for the C–N cross-coupling
reaction with aryl-halides and amines. The obtained MC-81 showed superior
performance compared with pristine TMU-81 and pyrolyzed P-TMU-81.
The catalysis performance is found to be closely dependent on the
amount of preloaded Cu2+ ions in the MOFs. After 5 cycles,
the catalysts were reusable without any significant loss of activity.
Benefiting from the structural and compositional advantages, the present
approach offers an intelligent way to synthesis and design of structurally
complex MOF hybrid and derived functionalized systems.