Pd(II)-immobilized on a nanoporous triazine-based covalent imine framework for facile cyanation of haloarenes with K₄Fe(CN)₆

A porous covalent organic framework incorporated with both imine and triazine functionalities (TPA-TCIF) was synthesized by Schiff-base condensation of 2,4,6-tris(4-aminophenyl)triazine and tris(4-formylphenyl)amine under the solvothermal condition of a 1-butanol:1,2-dichlorobenzene mixture. The resulting TPA-TCIF was a highly ordered crystalline network with surface area of 2938 m² g⁻¹, which was among the highest reported imine-based porous covalent organic frameworks. TPA-TCIF was also stable in water and other organic solvents. Pd(II) was immobilized into TPA-TCIF network and the resultant Pd/TPA-TCIF was tested as a catalyst for the additive-free cyanation of haloarenes with non-toxic K₄[Fe(CN)₆]. The catalyst showed excellent catalytic activity, and both electron-donating / -withdrawing groups attached to the para- and meta-positions of bromoarenes produced the respective nitriles with good to excellent yields. The catalyst could be reused up to five times without noticeable loss of activity or catalyst poisoning by cyanide ions during the reaction.