Synergistic Catalysis with MIL-101: Stabilized Highly Active Bimetallic NiPd and CuPd Alloy Nanoparticle Catalysts for C-C Coupling Reactions

Highly active bimetallic NiPd/MIL-101, CuPd/MIL-101 and CoPd/MIL-101 alloy nanoparticle catalysts stabilized by MIL-101 framework, (M/Pd atomic ratio = 95: 5, M = Ni, Cu and Co) were synthesized, and their catalytic activity for Suzuki reaction at moderate reaction conditions was explored. In contrary to monometallic counterparts, a significant enhancement in catalytic activity, with excellent yields for biaryls (upto 97%), was observed with these bimetallic NiPd/MIL-101, CuPd/MIL-101 and CoPd/MIL-101 alloy nanoparticle catalysts. Among these catalysts, NiPd/MIL-101 and CuPd/MIL-101 displayed highest catalytic activity for the synthesis of biaryls for a wide range of substituted aryl halides and arylboronic acids with electron donating and electron withdrawing substituents, whereas CoPd/MIL-101 was found to be poorly active. Worthy to mention that, NiPd/MIL-101 and CuPd/MIL-101 displayed ca 20 times higher TOF (h(-1)) than the Pd/MIL-101 catalyst. The observed high catalytic activity displayed by NiPd/MIL-101 and CuPd/MIL-101 was attributed to the synergistic effect due to electronic charge transfer from Ni or Cu to Pd, and high dispersion of NiPd and CuPd nanoparticles on MIL-101 frameworks.