Formation of a Highly Reactive Cobalt Nanocluster Crystal within a Highly Negatively Charged Porous Coordination Cage

Earth‐abundant first‐row transition‐metal nanoclusters (NCs) have been extensively investigated as catalysts. However, their catalytic activity is relatively low compared with noble metal NCs. Enhanced catalytic activity of cobalt NCs can be achieved by encapsulating Co NCs in soluble porous coordin...

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Bibliographic Details
Published in:Angewandte Chemie International Edition 2018-05, Vol.57 (19), p.5283-5287
Main Authors: Fang, Yu, Xiao, Zhifeng, Li, Jialuo, Lollar, Christina, Liu, Lujia, Lian, Xizhen, Yuan, Shuai, Banerjee, Sayan, Zhang, Peng, Zhou, Hong‐Cai
Format: Article
Language:English
Subjects:
ammonia–borane
Ammonium
Cages
Carbon dioxide
Catalysis
Catalysts
Catalytic activity
Cations
Cobalt
Confining
first-row transition metals
Heavy metals
hydrogen generation
Metals
metal–organic polyhedra
Nanoclusters
Noble metals
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Summary:Earth‐abundant first‐row transition‐metal nanoclusters (NCs) have been extensively investigated as catalysts. However, their catalytic activity is relatively low compared with noble metal NCs. Enhanced catalytic activity of cobalt NCs can be achieved by encapsulating Co NCs in soluble porous coordination cages (PCCs). Two cages, PCC‐2a and 2b, possess almost identical cavity in shape and size, while PCC‐2a has five times more net charges than PCC‐2b. Co2+ cations were accumulated in PCC‐2a and reduced to ultra‐small Co NCs in situ, while for PCC‐2b, only bulky Co particles were formed. As a result, Co NCs@PCC‐2a accomplished the highest catalytic activity in the hydrolysis of ammonium borane among all the first‐row transition‐metals NCs. Based on these results, it is envisioned that confining in the charged porous coordination cage could be a novel route for the synthesis of ultra‐small NCs with extraordinary properties. Does charge matter? The 30− charged anionic porous coordination cage PCC‐2a absorbs metal cluster precursors and reduces them within its cavity, yielding highly crystalline ultrafine Co nanoclusters. In contrast, 6− anionic PCC‐2b hardly encapsulates metal cluster precursors, leading to bulky and aggregated nanoclusters. The Co nanoclusters encapsulated by PCC‐2a show considerable activity improvement for the dehydrogenation of ammonia–borane.
ISSN:1433-7851
1521-3773
DOI:10.1002/anie.201712372