TiO₂@UiO-68-CIL: A Metal–Organic-Framework-Based Bifunctional Composite Catalyst for a One-Pot Sequential Asymmetric Morita–Baylis–Hillman Reaction

Abstract

A chiral ionic liquid (CIL) moiety of a Lpyrrolidin-2-ylimidazole-decorated homochiral UiO-68-type metal−organic framework, UiO-68-CIL (1), was successfully prepared by the combination of a new premodified chiral CIL ligand (H 2 L-CIL) and ZrCl 4 via a solvothermal method. The TiO 2 -loaded TiO 2 @UiO-68-CIL (2) was prepared by impregnating 1 in a toluene solution of Ti(OPr i ) 4 and sequential in situ hydrolysis. The obtained 2 can be a bifunctional asymmetric heterogeneous catalyst to successfully promote the one-pot Morita−Baylis−Hillman reaction starting from aromatic alcohols in a tandem way.

Chiral Metal–Organic Frameworks

“…Readily obtainable metal-free organocatalysts for highly efficient, sustainable, and practical asymmetric catalysis are equally sought after. − Specifically, enantioselective Brønsted acid catalysis has proved to be an outstanding approach in terms of both catalytic efficiency and stereoselectivity control. − This type of organocatalysts offers various activation modes in promoting efficient asymmetric formation of C–C and C–X (X = heteroatom) bonds and has achieved a massive development over the past decade. It is foreseeable that incorporating catalytically active organocatalysts into chiral frameworks can generate a number of CMOFs for enantioselective catalysis. ,,− As a matter of fact, Kim et al has thoroughly reviewed the progress of CMOF-based organocatalysis (including simple organocatalysis and privileged organocatalysis) in 2012 . However, little progress has been made in CMOF-based simple organocatalysis, which can be attributed to the established drawbacks of this approach proposed by Kim et al Therefore, the content of this section is limited to the CMOF-based privileged organocatalysis.…”

Applications of Nanomaterials in Asymmetric Photocatalysis: Recent Progress, Challenges, and Opportunities

“…Aside from the well‐studied asymmetric α‐alkylation of aldehydes, an efficient one‐pot sequential asymmetric Morita–Baylis–Hillman (MBH) reaction by chiral MOF‐based composite photocatalysts (TiO 2 @UiO‐68‐CIL) was reported by Dong and co‐workers very recently (Figure 5c). [ 71 ] In detail, the homochiral UiO‐68‐CIL was synthesized with l ‐pyrrolidin‐2‐ylimidazole chiral ionic liquid (CIL) modified ligand and ZrCl 4 via a solvothermal method. After then, the synthesized UiO‐68‐CIL was impregnated in a toluene solution of Ti(OPri) 4 and sequentially hydrolyzed to produce the TiO 2 ‐loaded TiO 2 @UiO‐68‐CIL composite.…”

Metal–Organic Framework UiO-68 and Its Derivatives with Sufficiently Good Properties and Performance Show Promising Prospects in Potential Industrial Applications

“…Here are some similar instances of metalation of UiO-68. TiO 2 @UiO-68-CIL (CIL: chiral ionic liquid) with a L-pyrrolidin-2-ylimidazole decorated reported also by Dong et al is an example that is similar to Pd(0)@UiO-68-AP, which can be a bifunctional asymmetric heterogeneous catalyst to promote the one-pot Morita–Baylis–Hillman reaction starting from aromatic alcohols in a tandem way . In another report, researchers make use of the postsynthetic exchange (PSE) method and tunable metallosalen-derived dicarboxylic ligands to produce single- and mixed-M­(salen)-linker (H 2 L M ) UiO-68-type crystals (M: Cu, Fe, Cr, Mn, V), which incorporate the same or different metal centers, shown in Figure . , Before the PSE, the as-synthesized ligand H 2 TPDC-Me is chosen because its length (15.3 Å) is similar to the H 2 L M (14.9 Å).…”