The development of uniformly distributed ultrafine metallic nanoclusters for advanced catalysts has attracted significant interest. However, synthesizing supports with specific electronic environments and well-defined pores to prevent aggregation remains challenging. Here, we report a facile palladium/copper cocatalyzed polycondensation to synthesize carbon-rich acetylenic nanostructures, poly(1,3,5-triethynylbenzene) (PTEB), for the in situ chelation of ultrafine Pd nanoclusters (∼0.4 nm). The extensive π-conjugated configuration of PTEB provides an electron-rich environment that enhances Pd coordination through charge transfer, while its intrinsic pore structures ensure exceptional Pd dispersibility and effective spatial confinement. This synergistic electronic and spatial design in Pd/PTEB catalysts exhibits impressive catalytic activities in liquid-phase reactions, achieving a remarkable turnover frequency of 15 039 mol_C=C mol_Pd^–1 h^–1 in the semihydrogenation of 1-octyne and a rate constant of 2.26 × 10⁷ min^–1 g_Pd^–1 for 4-nitrophenol reduction. These performances represent a significant improvement over commercial and previously reported Pd catalysts, demonstrating promising advances for stable and active heterogeneous catalysts.