A new type of pyrene–thiol derivative-modified Pd nanoparticle (NP) catalyst on a carbon black support for the efficient semihydrogenation of alkynes to alkenes is reported herein. Colloidal Pd NPs surrounded by pyrene–thiol modifiers were prepared using the two-phase Brust method followed by impregnation of carbon black materials. Based on the structural characterization of the prepared catalyst (PyC12S-Pd/VC) by NMR, UV–vis, FT-IR, TEM, HAADF-STEM, Pd K-edge XAFS, XRD, N2 adsorption, and XPS, we show that highly dispersed Pd NPs are immobilized on the catalysts via π–π interaction between pyrene groups bound to the Pd NPs and carbon black supports. PyC12S-Pd/VC efficiently catalyzes the alkyne semihydrogenation reaction while maintaining high alkene selectivity; an alkene selectivity of 94% is attained at 98% conversion after 5 h of reaction, and the selectivity was retained around 80% in 10 h of reaction. This performance is superior to that of a catalyst without pyrene groups and that of a commercial Lindlar catalyst. The steric hindrance of pyrene groups restricts access of the substrates to Pd NP surfaces, suppressing the unfavorable overhydrogenation of alkenes to alkanes, which is revealed by the solvent and substrate dependency on the catalytic performance and a DFT calculation study. Furthermore, the high selectivity and stability of PyC12S-Pd/VC are caused by the strong interaction between pyrene groups and carbon supports, which prevents the separation of pyrene modifiers and the leaching or sintering of Pd NPs during the catalytic reaction. It is demonstrated that the combination of Pd NPs, pyrene–thiol modifiers, and carbon supports offers high activity, alkene selectivity, and stability in the semihydrogenation reaction.

Aerobic oxidative dehydrogenation of amines to imines by thiol‐modified Pd nanoparticle (NP) catalysts on carbon supports is reported herein. Whereas conventional non‐modified Pd NP catalysts are nearly inactive, the carbon‐supported Pd catalysts modified with thiol ligands efficiently catalyze the reaction with high selectivity. Kinetic studies and DFT calculations reveal that the rate‐limiting imine product desorption step is significantly boosted on the thiol ligands‐modified Pd surface compared to the non‐modified Pd surface due to the steric hindrance of the ligands. Furthermore, the catalytic activity is dramatically enhanced in the presence of both pyrene‐functionalized thiol modifiers and graphene‐based carbon supports; 96 % conversion is attained after 4 h at 110 °C. The π–π interactions between pyrene groups and the highly crystallized carbon surface suppress the leaching of ligands, which offers improved catalyst stability even under O2 atmosphere at 110 °C, thereby resulting in high activity.

The Front Cover shows Pd nanoparticle catalysts modified with pyrene‐thiol ligands on carbon supports for aerobic oxidative dehydrogenation of amines to imines. In their Communication, T. Yoshii et al. experimentally and theoretically demonstrate that the rate‐limiting imine product desorption is boosted as a result of the steric hindrance of the ligands, and the catalytic stability is significantly improved by the π−π interactions between catalyst and support, which make this material an active and stable catalyst for the amine dehydrogenation reaction. This study provides a design guideline to unlock hidden catalytic properties of metal nanoparticles through surface modification. More information can be found in the Communication by T. Yoshii et al.