Abstract
Despite recent advances in the use of porous materials as efficient heterogeneous catalysts which operate through effectively trapping reagents in a well-defined space, continuously uptaking reagents to substitute products in the cavity for efficient product turnover still remains challenging. Here, a porous catalyst is endowed with ‘breathing’ characteristics by thermal stimulus, which can enable the efficient exchange of reagents and products through reversible stacking from inflated aromatic hexamers to contracted trimeric macrocycles. The contracted super-hydrophobic tubular interior with pyridine environment exhibits catalytic activity towards a nucleophilic aromatic substitution reaction by promoting interactions between concentrated reagents and active sites. Subsequent expansion facilitates the exchange of products and reagents, which ensures the next reaction. The strategy of mesoporous modification with inflatable transition may provide a new insight for construction of dynamic catalysts.
Highlights
Despite recent advances in the use of porous materials as efficient heterogeneous catalysts which operate through effectively trapping reagents in a well-defined space, continuously uptaking reagents to substitute products in the cavity for efficient product turnover still remains challenging
The expansion of transient states facilitates exchange of objects due to enhanced entropy in the aperture while the subsequent contraction accelerates effective collision between reagents[17,18]. These transient pores based on noncovalent interaction are too delicate to ensure effective exchange. Among these self-assembled systems, aromatic rod amphiphiles composed of conjugated carbon and hydrophilic dendritic segments can aggregate into porous structures with hydrophobic characteristics, which are well suitable as defined scaffolds for organic catalysis[19,20,21,22,23]
As hinted from recognition and regeneration of supramolecular apertures based on tunable assembly, we report a tubular catalyst with reversible contraction−expansion assembly for efficient exchange of products and reagents
Summary
Despite recent advances in the use of porous materials as efficient heterogeneous catalysts which operate through effectively trapping reagents in a well-defined space, continuously uptaking reagents to substitute products in the cavity for efficient product turnover still remains challenging. The walls of the tubules are fabricated through self-stacking of trimeric bent-shaped segments that are capable of readily inflating into hexameric macrocycles by thermo triggers (Fig. 1).
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