<p>Metal-organic frameworks (MOFs), composed of metal clusters and organic ligands, are highly ordered porous materials with diverse applications. Among these Al-MOFs are extensively studied as catalyst supports due to their stability and tunable properties. In this work, MIL-118/MIL-121 were employed as supports to synthesize Pd-HMIL-118/121 catalysts with hierarchical pore structures, which were tailored through thermal treatment. In the semi-hydrogenation of phenylacetylene, this catalyst exhibited outstanding activity and selectivity, which achieved a turnover frequency (TOF) of 154 mol_C=Cmol_Pd⁻¹min⁻¹, nearly 5-fold higher than that of the reported commercial Lindlar catalyst (33 mol_C=Cmol_Pd⁻¹min⁻¹). The catalyst demonstrated sustained structural stability and retained full activity over five consecutive cycles without reactivation. The pore structure evolution of MIL-118/121 was systematically characterized by using N₂ adsorption isotherms, X-ray diffraction, Fourier-transform infrared spectroscopy, electron microscopy, and thermogravimetric analysis. The results indicate that the mesopore ratio within the hierarchical pores initially increases and then decreases with prolonged thermal treatment, a trend that aligns with the catalytic performance in phenylacetylene semi-hydrogenation. The superior activity of Pd-HMIL-118/121 was attributed to the optimized mesopore formation via thermal treatment enhancing internal diffusion of phenylacetylene and styrene. The findings provide new insights into pore engineering strategies for MOF-based hydrogenation catalysts.</p> Graphical Abstract <p></p>