<p>CO esterification to dimethyl oxalate (DMO) plays a vital role in transforming inorganic C1 into organic oxygenated compounds. While Palladium (Pd)-based alumina catalysts exhibit excellent performance in this reaction, the regulation of active sites by alumina supports remains underexplored. To address this, two common types of alumina were used as supports for Pd-based catalysts prepared via the deposition-precipitation method. Notably, Pd nanoparticles (NPs)’ size was similar on both alumina supports, and the catalysts showed similar catalytic performance. The effect of calcination temperature was investigated: as the calcination temperature increased, the performance of the Pd/γ-Al₂O₃ catalyst gradually decreased, whereas that of the Pd/α-Al₂O₃ catalyst initially increased and then decreased. Further characterization confirmed that 1Pd-500/α-Al₂O₃ exhibited the more hollow CO on Pd, which corresponded to the better catalytic performance. Overall, this study illustrates that selecting a suitable alumina as the support and proper calcination temperature can cause Pd NPs having edge sites at a higher fraction for more hollow CO and improve catalytic performance of CO esterification to DMO.</p> Graphical Abstract <p></p>