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,β-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,β-enones were converted to chiral γ,δ-unsaturated ketones in medium to quantitative yields (40-98%) with high enantioselectivities (87-96% ee).
Abstract One‐pot production of sequence‐controlled block copolymer from mixed monomers is a crucial but rarely reached goal. Using a switchable Lewis‐pair organocatalyst, we have accomplished sequence‐selective polymerization from a mixture of O ‐carboxyanhydride (OCA) and epoxide. Polymerization of the OCA monomer occurs first and exclusively because of its exceedingly high polymerizability. When OCA is fully consumed, alternating copolymerization of epoxide and CO 2 liberated in OCA polymerization is triggered from the termini of the first block. The two polymerizations thus occur in tandem, both in chemoselective fashion, so that a sequence‐controlled block polymer with up to 99 % CO 2 conversion is furnished in this one‐pot protocol. Calculations and experimental results demonstrate a chemoselective and cooperative mechanism, where the high polymerizability of the OCA monomers guarantees exquisite sequence selectivity and the cooperative decarboxylation partly arose from the stabilization effect by triethylborane, which facilitates the smooth transformation of the chain end from carbonate to alkoxide.
In the past decades, the combination of supramolecular chemistry and catalysis has pushed forward the emergence of supramolecular catalysis as an intersectant and challenging research field. Supramolecular asymmetric catalysis has especially attracted growing attention attributing to their great advantages in both constructing chiral catalyst libraries and facilitating the improvement of catalytic activity and stereoselectivity, which promoted the development of green and sustainable chemistry. In this review, we summarize the progress on the supramolecular asymmetric catalysis involved crown ethers and their pseudorotaxanes and rotaxanes derivatives. The host–guest chemistry based on crown ethers has been successfully utilized to construct chiral catalysts or to regulate the asymmetric catalysis in both the metal and non-metal catalytic systems. The design and construction of supramolecular chiral catalysts, as well as their applications in catalyzing asymmetric reactions or modulating catalytic activity and stereoselectivity are systemically introduced.
Two-dimensional (2D) nanofluidics technology has shown great potential in efficient osmotic energy harvesting, while the lack of anion-selective 2D nanofluidics limits the development of full concentration cells towards real-world applications....
Abstract Developing high energy density lithium secondary batteries is pivotal for satisfying the increasing demand in advanced energy storage systems. Lithium metal batteries (LMBs) have attracted growing attention due to their high theoretical capacity, but the lithium dendrites issue severely fetter their real‐world applications. It is found that reducing anion migration near lithium metal prolongs the nucleation time of dendrites, meanwhile, promoting homogeneous lithium deposition suppresses the dendritic growth. Thus, regulating ion transport in LMBs is a feasible and effective strategy for addressing the issues. Based on this, a functional separator is developed to regulate ion transport by utilizing a well‐designed metal‐organic frameworks (MOFs) coating to functionalize polypropylene (PP) separator. The well‐defined intrinsic nanochannels in MOFs and the negatively charged gap channels both restricts the free migration of anions, contributing to a high Li + transference number of 0.68. Meanwhile, the MOFs coating with uniform porous structure promotes homogeneous lithium deposition. Consequently, a highly‐stable Li plating/stripping cycling for over 150 h is achieved. Furthermore, implementation of the separator enables LMBs with high discharge capacity, prominent rate performance and good capacity retention. This work is anticipated to aid developement of dendrite‐free LMBs by utilizing advanced separators with ion transport management.
In order to obtain effect of rotor rotation speed and inlet pressure on air mass flow rate distribution in various ducts of rotor of large turbo generators, the physical model of three-dimensional half axis rotor of 110MW air-cooling turbo-generator was created by the Gambit software. Then flow field of the model was simulated numerically according Finite Volume Method by the Fluent software. The effect of rotor rotation speed and inlet pressure on the distribution of air mass flow rate of axial inlet, end duct, sub-slot and radial ducts ventilation was analyzed. It shows that distribution of air flow rate in the rotor at actual working condition is different to experimental static condition and low inlet pressure condition.
Clay-based 2D nanofiltrations (NFs) have shown great potentials in wastewater treatment owing to their facile scale-up and low-cost feature. However, the swelling effect seriously limits their separation efficient towards the construction of high-performance NFs. Herein, an anti-swelling clay-based 2D NF is developed based on the strategy of electrostatic interlamellar fixation. The intercalation of positively-charged Fe(OH)3 nanoparticles could effectively fix the interlayer spacing of negatively-charged montmorillonite-based 2D NF, contributing to a high dye (Congo red) retention rate up to 99.78% and also a satisfactory flux of 60.65 L m−2 h−1 bar−1 and a separation mechanism that proposes a combined effect of size, electrostatic potential, and conjugation for a variety of dyes. When scaling up (~700 cm2), the anti-swelling 2D NF still maintain an excellent separation effect that is superior to almost all reported state-of-the-art 2D NFs. According to the detailed life cycle assessments (LCA), the utilization of 2D clay material also exhibits superior resource, environmental and techno-economic benefits compared to other mainstream 2D materials. This work proposes an effective strategy to solve the swelling effect of clay-based 2D NFs towards the large-scale utilization of high-performance and low-cost separation membrane for efficient wastewater treatment.
Abstract Inspired from dynamic living systems that operate under out‐of‐equilibrium conditions in biology, developing supramolecular hydrogels with self‐regulating and autonomously dynamic properties to further advance adaptive hydrogels with life‐like behavior is important. This review presents recent progress of bio‐inspired supramolecular hydrogels out‐of‐equilibrium. The principle of out‐of‐equilibrium self‐assembly for creating bio‐inspired hydrogels is discussed. Various design strategies have been identified, such as chemical‐driven reaction cycles with feedback control and physically oscillatory systems. These strategies can be coupled with hydrogels to achieve temporal and spatial control over structural and mechanical properties as well as programmable lifetime. These studies open up huge opportunities for potential applications, such as fluidic guidance, information storage, drug delivery, actuators and more. Finally, we address the challenges ahead of us in the coming years, and future possibilities and prospects are identified.
Supramolecular asymmetric catalysis has arisen from the in-depth intersection of supramolecular chemistry and asymmetric catalysis due to its unique advantages in building chiral catalyst libraries and regulating performance of catalysts. Herein, we combine crown ether based host-guest chemistry with chiral phosphoric acid mediated asymmetric catalysis to actualize the supramolecular regulation of catalytic asymmetric two-component tandem acetalization reactions. By comparison with the catalytic reaction without host-guest interaction, improvement of up to 72% in yield and increases of up to 13% in enantioselectivity were acquired after addition of the alkali metal guests, which demonstrated the great advantages of this supramolecular regulation strategy.
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