Stepwise and Controllable Synthesis of Mesoporous Heterotrimetallic Catalysts Based on Predesigned Al₄Ln₄ Metallocycles

Abstract

The motivation for making heterometallic compounds stemmed from their emergent synergistic properties and enhanced capabilities for applications. However, the atomically precisely controlled synthesis of heterometallic compounds remains a daunting challenge of the complications that arise when applying several metals and linkers. Herein, a stepwise and controlled method is reported for the accurate addition of second and third metals to homometallic aluminum macrocycles based on the synergistic coordination and hard‐soft acid‐base theory. These heterometallic compounds showed a good Lewis acid catalytic effect, and the addition of hetero‐metals significantly improved the catalytic effect and rate, among that the conversion rate of compound AlOC‐133 reached 99.9% within half an hour. This method combines both the independent controllability of stepwise assembly with the universality of one‐step methods. Based on the large family of clusters, the establishment of this method paves the way for the controllable and customized molecular‐level synthesis of heterometallic materials and creates materials customized for preferential application.

Induced Aggregation, Solvent Regulation, and Supracluster Assembly of Aluminum Oxo Clusters

“…Recently, we found that metal ions with large radii and high coordination numbers like Ln ions could be stable in the middle of the ring via coordination bonds . Besides, heterometallic Al 4 Ln 4 rings are isolated by the employment of amino-polyalcohol …”

“…The binding sites between aluminum molecular rings and substrates can be crystallographically characterized and theoretically confirmed, providing a reliable basis for understanding the mechanism of cyanosilylation. The incorporation of lanthanide Lewis acid sites further facilitates the reaction and reaches a production of nearly 100% . In addition, transitional metal centers with unsaturated coordination sites employed facilitate interaction with substrate acetone and thus possess aldol condensation catalytic activity. − Based on the solubility and stability of clusters, our group investigated their homogeneous and heterogeneous catalytic performances, utilizing the solvent effect and supramolecular effect, inducing a high catalytic conversion efficiency for β-hydroxy ketone and α,β-unsaturated ketone …”

Synthesis and photoluminescence properties of polymer chains based on pre-designed heterometallic Al4Ln4 molecular rings

“…Aluminum and rare earth element co-constructed structures have attracted attention because of both the high stability of aluminum and the functionality of rare earth elements in catalysts, 1–3 optics 4–7 and magnetism. 8–10 As early as 1997, La[Al(O i Pr) 4 ] 3 has been used in the sol–gel synthesis of high specific surface area LaAlO 3 for automotive catalytic converters.…”

“…21,22 Furthermore, catalysts have been developed in the form of three hat-shaped cationic Al 9 Ln 7 3 and neutral octanuclear ring Al 4 Ln 4 . 2…”

“…In our previous work, heterometallic Al 4 Ln 4 octanuclear rings were synthesized using N -methyldiethanolamine (H 2 MDEA) in combination with aromatic carboxylate ligands. 2 Their extended frameworks were constructed by introducing a third metal (Cu) whose heterometallic ring units are linked by coordination bonds. 2 As a continuation of our work, we herein report a chain-like compound ( AlOC-195 ) formed by formic acid-bridged heterobimetallic molecular ring Al 4 Ln 4 (Fig.…”