Modulating the Performance of an Asymmetric Organocatalyst by Tuning Its Spatial Environment in a Metal–Organic Framework

Abstract

Systematically tuning the spatial environment around the active sites of synthetic catalysts is a difficult challenge. Here, we show how this can be accomplished in the pores of multicomponent metal-organic frameworks. This relies on embedding a catalytic unit in a pore of the MUF-77 framework and then tuning its environment by introducing different functional groups to the surrounding linkers. This approach benefits from the structural regularity of MUF-77, which places each component in a precise location to circumvent disorder. Prolinyl groups, which are catalytically competent toward asymmetric aldol reactions, were selected as the catalytic unit. Since every prolinyl group is positioned in an identical environment, correlations between the pore architecture and the activity of these single-site catalysts can be elucidated. Systematic engineering of the pore structure, which is achieved by installing modulator groups on the framework linkers, impacts on the reaction rate and the enantiomeric excess of the aldol products. Furthermore, the spatial environment around the proline catalyst can override its innate stereochemical preference to dictate the preferred enantiomer of the reaction product. These results offer a new way to design three-dimensional active site environments for synthetic catalysts.

Porous Metal‐Organic Polyhedral Framework containing Cuboctahedron Cages as SBUs with High Affinity for H2 and CO2 Sorption: A Heterogeneous Catalyst for Chemical Fixation of CO2

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Development of activep orous materials that can efficiently adsorb H 2 and CO 2 is needed, due to their practical utilities. [6][7][8] The special feature of the MOFs, compared to traditional zeolites, is that they can be tailor made by introducing organic moieties for targeted absorption of gases. The Cu II -MOF containsa highly symmetric polyhedral metal cluster (Cu 24 )w ith cuboctahedron geometry as secondary building unit (SBU).

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van der Waals Epitaxial Growth of 2D Metal–Porphyrin Framework Derived Thin Films for Dye‐Sensitized Solar Cells

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nature, which cannot meet the increasing demand for its broad applications in DSSCs. [8,9] Metal-organic frameworks (MOFs) represent a class of porous coordination polymers that consist of organic ligands linker by metal ions to form crystalline assemblies, [10,11] which have been widely investigated for their attractive physical and chemical properties. [8,9] Metal-organic frameworks (MOFs) represent a class of porous coordination polymers that consist of organic ligands linker by metal ions to form crystalline assemblies, [10,11] which have been widely investigated for their attractive physical and chemical properties.

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Asymmetric Catalysis within the Chiral Confined Space of Metal–Organic Architectures

“…To fabricate second‐generation organocatalytic MOFs with improved enantioselectivities, later works from the same group clearly demonstrated that systematically tuning the spatial environment around the active sites of the synthetic catalysts in the pores of multicomponent MOFs may lead to an improvement of enantioselectivities. They successfully embedded chiral prolinyl catalytic units in the pore of the M2 framework by covalently binding it to distinct ditopic linkers, 1,4‐benzenedicarboxylate ( L 10 ‐H 2 bdc) and 4,4′‐biphenyldicarboxylate ( L 10 ‐ H 2 bpdc), and then tuning its environment by introducing a tritopic truxene ( L 11 ) or other ditopic modulators.…”

“…c) Aldol reaction of acetone and p ‐nitrobenzaldehyde catalyzed by M2 analogues with installed bdc‐Pro linkers. Reproduced with permission . Copyright 2017, American Chemical Society.…”