Interstitial Modification of PdNi Nanoalloy with Boron Atoms for Reductive Homocoupling of Furfural Derivatives

Furfural-based bifuran diacids/diesters, such as 2,2′-bifuran-5,5′-dicarboxylic acid (BFDCA), are important biomass-derived chemicals in the production of high-performance polymers and plasticizers. However, the synthesis of bifuran diacids/diesters lacks an efficient heterogeneous catalytic system. Here, we report that the interstitial modification of a PdNi bimetallic nanoalloy with boron atoms supported on nitrogen-doped carbon exhibited high catalytic efficiency in the conversion of halogenated furoic acids/esters to bifuran diacids/diesters via sequential oxidative addition and reductive elimination steps initiated at room temperature, affording a high yield with a Pd/Ni molar ratio of 1:1. The conversion of 5-bromo-2-furoic acid to BFDCA has a turnover frequency value of up to 672.0 h–1, 2.5 times higher than that of commercial Pd/C. The comprehensive characterization results demonstrated that boron as an interstitial atom entered into the lattice of the PdNi alloy, leading to lattice distortion and the regulation of the electronic state of Pd. Density functional theory calculations exhibited that these electronegative Pd sites were pivotal active species in the oxidation addition, where Ni facilitated the coordination of Pd and carbon–halogen bonds. The optimal catalyst showed excellent stability and recyclability in alkaline aqueous solution. This protocol provides an efficient strategy for the reductive homocoupling and sustainable production of bifuran diacids/diesters and their derivatives from biomass resources.