The construction of Csp3-Csp3 with high stereoselectivity, even in a stereodivergent way, has been a long-standing theme in organic synthesis. As an atom- and step-economic transformation, transition metal hydride-mediated allylic alkylation of enolizable carbonyl compounds with readily available allenes, alkynes or 1,3-dienes as the unconventional allylating reagents has recently emerged as a promising protocol for the stereoselective construction of Csp3-Csp3 bonds with high efficiency. Due to their less enolizability and weak nucleophilicity, simple esters remain challenging substrates for these coupling reactions. On the other hand, the strategy of metal/organo combined catalysis has recently emerged as one of the wide-ranging disciplines and powerful tools in asymmetric synthesis. Considering the recent achievements of chiral Lewis base catalysis in catalytic asymmetric α-functionalization of esters through a “rebound” mechanism, the cooperative combination of chiral Lewis bases and metal hydride catalysis may offer great opportunities to the aforementioned chemistry. Recently, the groups of Snaddon and Zi have made remarkable progresses in this area through palladium and chiral Lewis base cooperative catalysis.
Carbocatalysts, as a member of metal-free catalysts, have shown promising potentials in many catalytic transformations in the past few decades. Nitrogen doping has been identified as an effective way to tailor the properties of carbocatalysts and render their potential use for various applications. It is also important to fabricate unique surface compositions or properties for the N species to enhance their intrinsic catalytic activities. Hybrid
Described here is the first deracemization of triaryl-substituted carbon stereocenters, which is in contrast to the well-established processes to deracemize monoaryl- and diaryl-substituted ones. This one-pot redox process involves in situ generation of a para-quinone methide intermediate followed by asymmetric reduction by chiral phosphoric acid catalysis. A wide range of highly enantioenriched triarylmethanes could be generated with high efficiency under mild conditions.
Transitional metal single atom (TM1) doped graphene catalysts have been widely applied in electrochemical N2 reduction reaction (NRR). However, it remains a challenge for the rational design of highly active and selective electrocatalysts owing to limited knowledge of structure-activity correlations. Here, we adopted first-principle calculations to high-throughput screen the NRR performance of TM1 coordinated with two boron and two nitrogen atoms in graphene (TM1-B2N2/G). A “five-step” strategy was implemented by progressively considering different metrics such as stability, N2 adsorption, N2 activation, potential-determining step, and selectivity. As a result, a volcano plot of reactivity is established by using the valence electron number of TM1 as the descriptor. Among all catalysts, Cr1-B2N2/G exhibits superior performance with a limiting potential of -0.43 V with high selectivity of NRR interpreted by better spatial symmetry and excellent compatibility in terms of energy when N2 interacts with TM1. Our work reveals the general strategy of computational efforts to predict the next generation of advanced catalytic materials for NRR.
Supported noble metal catalysts have exhibited satisfactory catalytic performance in the dehydrogenation of liquid chemical hydrogen carriers, in which the supports play a paramount role in conditioning the nature of the active center and thus improving the overall reactivity. Herein, the specially designed nitrogen/amino co-functionalized carbon (NH2-NC) supports are prepared to load active Pd nanoclusters for efficient dehydrogenation of formic acid (FA). The nitrogen/amino co-functionalization of carbon not only facilitates the Pd nanoclusters evenly dispersed with a mean size of 1.4 nm, but also provides a beneficial metal-support interaction to promote FA dehydrogenation. The as-prepared Pd@NH2-NC discloses a 100% conversion of FA into CO2 and H2 with a remarkable initial turnover frequency (TOFinitial) of 4,892 h-1 and a low activation energy (Ea) of 28.5 kJ mol-1 without additive at 298 K. The work proposes a co-functionalization strategy to reasonably design supports for heterogeneous catalysts and may be extended to develop other multi-functionalized supports with different compositions and nanostructures.
Biotransformation of natural, synthetic, and semi-synthetic compounds has emerged as a frontier branch of chemical sciences that is progressively being applied in numerous fields. In the present review, we have summarized our biotransformation studies on bioactive compounds from 1997 to 2022. Various microbial and plant cell cultures were used for biocatalytic structural transformations. We present here an overview of biotransformation of 53 compounds belonging to various classes of natural, synthetic, and semi-synthetic compounds, published in several leading journals. The structures of the resulting metabolites have been elucidated by detailed spectroscopic studies. Oxidation, reduction, dehydrogenation, chlorination, aromatization, methylation, demethylation, rearrangements, etc. were the main reactions that occurred during the biotransformation processes. Many of the biotransformed products exhibited interesting biological activities. Structural transformations in some cases have also led to improved pharmacokinetic profiles. This review is aimed to provide a focused account of extensive work carried out in our laboratories in this field, as well as the immense potential of biocatalytic transformations in organic chemistry.
Copper-based chalcogenide compounds have emerged as alternative materials to Cd- or Pb-based traditional semiconductors and have drawn significant attention. Compared with widely reported semiconductors, copper chalcogenide nanocrystals (NCs) with abundant copper defects and vacancies present p-type features. Additionally, the migration of free hole carriers in copper-based chalcogenide NCs produced a metal-like local surface plasmon resonance (LSPR) effect. In this review, we focused on the plasmonic copper chalcogenide NCs achieved through a heavily doped strategy. The copper sulfur compounds with versatile atomic ratios and complex crystal structures exhibit rich electrical, optical, and magnetic properties, making them highly promising for a broad range of applications, from energy conversion to biomedical fields. Therefore, our main focus is on the classification of copper chalcogenide synthesis strategies, theoretical studies of doping, doping strategies, and biological applications. We aim to analyze the trends of copper-based chalcogenide nanomaterials for clinical applications by summarizing previous studies and presenting designs and concepts in a brief manner.
Signaling dynamic networks in living systems determine the conversion of environmental information into biological activities. Systems chemistry, focusing on studying complex chemical systems, promotes the connections between chemistry and biology and provides a new way to mimic these signaling dynamic processes by designing artificial networks and understanding their emerging properties and functions that are absent in isolated molecules. Nucleic acids, while relatively simple in their design and synthesis, encode rich structural and functional information in their base sequence, which makes them an ideal building block for constructing complex dynamic networks that can mimic those in living systems. This review briefly introduces nucleic acid-based dynamic networks that can mimic natural signaling dynamic processes. We summarize how the nucleic acid-based dynamic networks are utilized to mimic relatively simple biological transformations, such as feedback and feedforward, which act as sub-networks to produce complex dynamic behaviors upon collective integration. We also emphasize the recent development of far-from-equilibrium networks, which are designed for converting the spatiotemporal signal and coupling with the downstream systems to achieve different functionalities and applications, including temporary nanostructure and patterns, programmed catalysis, and more, using nucleic acid-based dynamic networks. We also address the challenges of developing nucleic acid-based dynamic networks by directed evolution, operating complex networks under confinement conditions, and integrating multiplex networks into cell-like containments aiming to create protocells with living features.
Intermetallics are a large family of structurally ordered alloys that combines a metal element with other metal/metalloid elements with a clearly defined stoichiometric ratio. Intermetallics possess abundant crystal structures and atomic packing motifs, giving rise to a great variety of electronic configurations and surface adsorption properties. The wide electronic and geometric diversity makes intermetallics a highly promising population for discovering advanced materials for various catalytic applications. This review presents recent advances in the reaction synthesis of intermetallic materials at the nanoscale and their energy-related electrocatalytic applications. Initially, we introduce general principles for the formation of stable intermetallic structures. Subsequently, we elaborate on common synthetic strategies of nanostructured intermetallics, such as thermal annealing, wet-chemical methods, metallothermic reduction, and template-directed synthesis. Furthermore, we discuss the wide employment of these intermetallic nanocatalysts in many different kinds of electrocatalytic applications, as well as highlight the theoretical and experimental evidence for establishing a reasonable relationship between atomic arrangement and catalytic activity. Finally, we propose some perspectives for future developments of intermetallic preparation and catalytic applications.
Core-shell structures are widely used to modulate upconversion emission or mitigate surface quenching and cross-relaxation in lanthanide-doped upconversion nanoparticles (UCNPs) to meet the requirements of various applications. Interfacial cation migration has been found recently to deteriorate the core-shell structures and thus affect their upconversion luminescence when they are subjected to annealing post-treatment. Herein, we demonstrate that the interfacial cation migration largely depends on the crystalline phase of the host lattice. Significant Er3+/Y3+(Yb3+) diffusion and migration occur across the core-shell interface when cubic NaREF4 (RE = Y, Yb, Er) core-shell or core-shell-shell UCNPs are annealed at 200 °C in the solid state, while the cation migration in hexagonal counterparts is negligible and the core-shell (core-shell-shell) structure can be well maintained in the same condition. The loosely packed atoms and large cubic void surrounded by eight F- ions in cubic NaREF4 lattice may facilitate cations diffusion and migration, enabling interfacial cations migration at relatively lower temperature. This finding may help us better understand temperature-dependent upconversion luminescent properties of core-shell UCNPs and better utilize various core-shell structured UCNPs according to different requirements of applications.
Lithium-selenium (Li-Se) batteries have attracted much attention in recent years because of their high volumetric capacity (3253 mA h cm-3) compared to the current commercial Li-ion battery. The shuttle effect and large volume variation during the electrochemical reactions limit its practical applications. The widely accepted strategy to reduce these drawbacks is confining selenium (Se) in porous carbon materials. However, how to boost electrochemical kinetics, reduce the shuttle effect and accommodate volume expansion for maximized battery performance still remains highly challenging. Herein, we synthesized three kinds of hierarchically porous carbon materials by facile pyrolysis of aluminum-based metal-organic frameworks (MOFs) with different porous networks. The large surface area and high pore volume can ensure the excellent polyselenides adsorption while tailoring the ratio between micropores and mesopores of the hierarchically porous hosts can highly enhance electrolyte and electron transportation, leading to excellent electrochemical performance with a capacity as high as 530.1 mA h g-1 (Se@MIL-68-800) after 200 cycles, an excellent rate capability of 307 mA h g-1 at 5 C, and a high reversible capacity of 544 mA h g-1 when current density returns to 0.1 C. The present invention not only provides a facile way to obtain hierarchically porous carbon materials from MOFs but also gives insights on tailoring micropores and mesopores proportion to maximize Li-Se battery performance for their practical industrial implementation.