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1.
ChemSusChem ; 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-33258550

RESUMO

Lithium-sulfur battery (LSB) has become one of the most promising candidates for next-generation energy storage systems owing to its high theoretical energy density, environmental friendliness, and cost-effectiveness. However, its real-word applications are seriously restricted by its undesirable shuttle effect and lithium (Li) dendrite formation. In essence, uncontrollable anion transport is a key factor that causes both polysulfide shuttling and dendrite formation, which creates the possibility of simultaneously addressing the two critical issues in LSBs. An effective strategy to control anion transport is the construction of cation-selective separators. A significant progress has been achieved in the inhibition of the shuttle effect, whereas addressing the problem of Li dendrite formation by utilizing a cation-selective separator is still underway. From this viewpoint, this review analyzes the critical issues with regard to the shuttle effect and Li dendrite formation caused by uncontrollable anion transport, based on which the roles and advantages of cation-selective separators toward high-performance LSBs are presented. According to the separator construction principle, the latest advances and progress in cation-selective separators in inhibiting the shuttle effect and Li dendrite formation are reviewed in detail. Finally, some challenges and prospects are proposed for the future development of cation-selective separators. This review is anticipated to provide a new perspective for simultaneously addressing the two critical issues in LSBs.

2.
J Am Chem Soc ; 142(23): 10244-10249, 2020 Jun 10.
Artigo em Inglês | MEDLINE | ID: mdl-32433874

RESUMO

Introducing self-assembly strategies into the construction of catalysts has been proven to have great advantages in asymmetric catalysis. We constructed two chiral metalla-triangles by highly efficient coordination-driven self-assembly from a chiral 3,3'-dipyridyl-substituted BINOL donor. They were successfully applied in asymmetric conjugate addition of a series of α,ß-unsaturated ketones with trans-styrylboronic acids. The use of these metalla-triangles as supramolecular catalysts is obviously conducive to the enhancement of catalytic activity and stereoselectivity in the presented addition reactions. Under induction of the chiral metalla-triangles, an array of α,ß-enones were converted to chiral γ,δ-unsaturated ketones in medium to quantitative yields (40-98%) with high enantioselectivities (87-96% ee).

3.
J Am Chem Soc ; 141(1): 281-289, 2019 01 09.
Artigo em Inglês | MEDLINE | ID: mdl-30511838

RESUMO

Ring-opening polymerization of O-carboxyanhydrides (OCAs) can furnish polyesters with a diversity of functional groups that are traditionally hard to harvest by polymerization of lactones. Typical ring-opening catalysts are subject to unavoidable racemization of most OCA monomers, which hampers the synthesis of highly isotactic crystalline polymers. Here, we describe an effective bifunctional single-molecule organocatalysis for selective ring-opening polymerization of OCAs without epimerization. The close vicinity of both activating groups in the same molecule engenders an amplified synergetic effect and thus allows for the use of mild bases, thereby leading to minimal epimerization for polymerization. Ring-opening polymerization of manOCA monomer (OCA from mandelic acid) mediated by the bifunctional single-molecule organocatalyst yields highly isotactic poly(mandelic acid) (PMA) with controlled molecular weights (up to 19.8 kg mol-1). Mixing of the two enantiomers of PMA generates the first example of a crystalline stereocomplex in this area, which displayed distinct Tm values around 150 °C. Remarkably, the bifunctional catalysts are moisture-stable, recyclable, and easy to use, allowing sustainable and scalable synthesis of a stereoregular functional polyester.

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