Targeted Conversion of Biomass into Primary Diamines via Carbon Shell-Confined Cobalt Nanoparticles

Abstract

Primary diamines are valuable yet challenging to synthesize due to issues such as product and intermediate condensation and catalyst poisoning. To address these problems, effective synthesis systems must be explored. Here, 2,5-bis(aminomethyl)furan (BAMF), a biomass-derived primary diamine, is chosen as the model for constructing such a system. A series of carbon-shell confined Co nanoparticles (Co@CNT-x) are fabricated to synthesize BAMF. The Co@CNT-700 catalyst, with ca. 4 layers of carbon shells, achieves an outstanding 96% isolated yield of BAMF through the reductive amination of 2,5-diformylfuran dioxime. In this system, an excess NH₃ atmosphere is necessary to prevent condensation reactions by competitive reactions, while the carbon shells protect the catalyst from NH₃ and amine poisoning. Control experiments indicate that 2,5-diformylfuran dioxime primarily follows a H₂-assisted dehydration pathway to form key imine intermediates, while side products such as amides and nitriles can also eventually be converted into BAMF by Co@CNT-700, leading to its excellent selectivity. Notably, by employing a sequential three-step strategy, ca. 87% BAMF can be achieved by directly using biomass as the raw material. To evaluate the tolerance of this system, 9 other important aromatic, cycloalkyl, and linear alkyl primary diamines, such as 1,4-cyclohexanediamine, are obtained in high yields of 87−99%.