The classic Fokin mechanism of the CuAAC reaction of terminal alkynes using a variety of Cu(I) catalysts is wellknown to include alkyne deprotonation involving a bimetallic sigma,pi-alkynyl intermediate. In this study, we have designed a CNT-supported atomically precise nanocluster Au4Cu4 (noted Au4Cu4/CNT) that heterogeneously catalyzes the CuAAC reaction of terminal alkynes without alkyne deprotonation to a sigma,pi-alkynyl intermediate. Therefore, three nanocluster-pi-alkyne intermediates [Au4Cu4(pi-CH C-p-C6H4R)], R = H, Cl, and CH3, have been captured and characterized by MALDI-MS. This Au4Cu4/CNT system efficiently catalyzed the CuAAC reaction of terminal alkynes, and internal alkynes also undergo this reaction. DFT results further confirmed that HC CPh was activated by pi-complexation with Au4Cu4, unlike the classic dehydrogenation mechanism involving the bimetallic sigma,pi-alkynyl intermediate. On the other hand, a Cu-11/CNT catalyst was shown to catalyze the reaction of terminal alkynes following the classic deprotonation mechanism, and both Au-11/CNT and Cu-11/CNT catalysts were inactive for the AAC reaction of internal alkynes under the same conditions, which shows the specificity of Au4Cu4 involving synergy between Cu and Au in this precise nanocluster. This will offer important guidance for subsequent catalyst design.