A partial ligand exchange strategy for fabricating catalytically active single palladium site immobilized on zeolitic imidazolate framework-8 (ZIF-8, Pd₁/ZIF-8) is proposed in this work. The one-step synthesis simply involves reacting Na₂PdCl₄ with ZIF-8 in solvent. The Cl ligands of Na₂PdCl₄ exchanged with 2-methylimidazole (2-MeIm) of the framework, resulting in the anchoring Pd on the framework and dissociation of Zn into the solution. The whole synthesis is performed at ambient conditions and the crystalline integrity of ZIF-8 is well retained. The resulting Pd₁/ZIF-8 is extensively characterized by different techniques which confirm the proposed mechanism. Pd₁/ZIF-8 is also successfully applied in the size-selective semi-hydrogenation of alkynes.