Heterogeneous catalysts with precise surface and interface structures are of great interest to decipher the structure–property relationships and maintain remarkable stability while achieving high activity. Here, we report the design and fabrication of the new sandwich composites ZIF-8@Au25@ZIF-67[tkn] and ZIF-8@Au25@ZIF-8[tkn] [tkn = thickness of shell] by coordination-assisted self-assembly with well-defined structures and interfaces. The composites ZIF-8@Au25@ZIF-67 efficiently catalyzed both 4-nitrophenol reduction and terminal alkyne carboxylation with CO2 under ambient conditions with remarkably improved activity and stability, compared to the simple components Au25/ZIF-8 and Au25@ZIF-8, highlighting the highly useful function of the ultrathin shell. In addition, the performances of these composite sandwich catalysts are conveniently regulated by the shell thickness. This concept and achievements should open a new avenue to the targeted design of well-defined nanocatalysts with enhanced activities and stabilities for challenging reactions.
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 σ,π-alkynyl intermediate. In this study, we have designed a CNTsupported atomically precise nanocluster Au 4 Cu 4 (noted Au 4 Cu 4 /CNT) that heterogeneously catalyzes the CuAAC reaction of terminal alkynes without alkyne deprotonation to a σ,π-alkynyl intermediate. Therefore, three nanocluster−π-alkyne intermediates [Au 4 Cu 4 (π-CHC-p-C 6 H 4 R)], R = H, Cl, and CH 3 , have been captured and characterized by MALDI-MS. This Au 4 Cu 4 /CNT system efficiently catalyzed the CuAAC reaction of terminal alkynes, and internal alkynes also undergo this reaction. DFT results further confirmed that HCCPh was activated by π-complexation with Au 4 Cu 4 , unlike the classic dehydrogenation mechanism involving the bimetallic σ,π-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 Au 4 Cu 4 involving synergy between Cu and Au in this precise nanocluster. This will offer important guidance for subsequent catalyst design.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.