An interfacial synergism effect of Pd–g-C3N4 in Pd/g-C3N4 for highly active and selective hydrogenation of 4-nitrophenol

Herein, we report that Pd nanoparticles (NPs) anchored on graphitic nitride carbon (Pd/g-C₃N₄) catalysts with various Pd contents (1.55 wt%, 0.14 wt%, 0.04 wt%) are successfully prepared via a simple NaBH₄ reduction method, exhibiting excellent catalytic activity and selectivity toward 4-aminophenol (4-AP) in 4-nitrophenol (4-NP) selective hydrogenation. 4-NP is completely converted to 4-AP (yield ∼ 100%) under quite moderate reaction conditions (40 °C, 2.0 MPa H₂ and 5 min) over the 1.55 wt% Pd/g-C₃N₄ catalyst, with a high reaction rate r = 134.4 mol_4-NP mol_Pd⁻¹ min⁻¹. The excellent catalytic performance can be attributed to the following reasons: (1) a higher ratio of Pd(0)/Pdⁿ⁺ provides much more exposed active sites for the potential adsorption and activation of the reactants, which is beneficial for increasing the reaction rate and catalytic activity; (2) Pd NPs are highly dispersed on g-C₃N₄ due to the strong interaction of Pd–N or Pd–C; (3) the interfacial synergism effect between Pd NPs and g-C₃N₄ enables the effective adsorption and activation of H₂ (4-NP) at Pd (g-C₃N₄), promoting the catalytic hydrogenation of 4-NP and improving their catalytic properties. In addition, this catalyst has superior reusability.