Regulating Lewis acid–base sites in catalysts to investigate their influence in the chemical fixation of CO2 is significant but challenging. A metal–organic framework (MOF) with open metal Co sites, ...{(NH2Me2)Co3(μ3‐OH)(BTB)2(H2O)⋅9 H2O⋅5 DMF}n (1), was obtained and the results of the catalytic investigation show that 1 can catalyze cycloaddition of CO2 and aziridines to give 99 % yield. The efficiency of the cyclization of CO2 with propargyl amines is only 32 %. To improve the catalytic ability of 1, ligand XN with Lewis base sites was introduced into 1 and coordinated with the open Co sites, resulting in a decrease of the Lewis acid sites and an increase in the Lewis base sites in a related MOF 2 ({(NH2Me2)Co3(μ3‐OH)(NHMe2)(BTB)2(XN)⋅8 H2O⋅4 DMF}n). Selective regulation of the type of active centers causes the yield of oxazolidinones to be enhanced by about 2.4 times, suggesting that this strategy can turn on/off the catalytic activity for different reactions. The catalytic results from 2 treated with acid solution support this conclusion. This work illuminates a MOF‐construction strategy that produces efficient catalysts for CO2 conversion.
Selective regulation of Lewis acid–base sites in metal–organic framework catalysts is an effective strategy to turn‐on/off the catalytic activity for different CO2 reactions.
Owing to their permanent porosity, highly ordered and extended structure, good chemical stability, and tunability, covalent organic frameworks (COFs) have emerged as a new type of organic materials ...that can offer various applications in different fields. Benefiting from the huge database of organic reactions, the required functionality of COFs can be readily achieved by modification of the corresponding organic functional groups on either polymerizable monomers or established COF frameworks. This striking feature allows homochiral covalent organic frameworks (HCCOFs) to be reasonably designed and synthesized, as well as their use as a unique platform to fabricate asymmetric catalysts. This contribution provides an overview of new progress in HCCOF‐based asymmetric catalysis, including design, synthesis, and their application in asymmetric organic synthesis. Moreover, major challenges and developing trends in this field are also discussed. It is anticipated that this review article will provide some new insights into HCCOFs for heterogeneous asymmetric catalysis and help to encourage further contributions in this young but promising field.
Chirality from COFs: Owing to their permanent porosity, highly ordered and extended structure, good chemical stability, and tunability, covalent organic frameworks have emerged as a new type of organic materials that can offer various applications in different fields. Herein, the design and synthesis of chiral covalent organic frameworks and their applications in asymmetric catalysis are highlighted.
Postsynthetic modification (PSM) has been demonstrated to be a powerful method for achieving new covalent organic frameworks (COFs) via single-step or multistep organic functional group ...transformations on established COF frameworks. PSM, however, might sometimes lead to collapse of the COF framework, decreases in crystallinity, or low postsynthetic yield due to the inherent limit of solid-state synthesis. Herein we report, for the first time, a new synthetic strategy that can generate new COFs via multicomponent one-pot in situ reactions. In total, 12 α-aminonitrile- and quinoline-linked COFs with high crystallinity and permanent porosity are successfully achieved by three-component one-pot in situ Strecker and Povarov reactions under solvothermal conditions in high yields. The obtained COFs feature the same structures as those obtained from the stepwise PSM approach on an established imine-linked COF. This in situ multicomponent assembly strategy, as a synthetic methodology parallel to PSM, might open a new route for constructing COFs that is not possible under PSM conditions.
Astrocytes metabolically interact with neighboring neurons by providing multiple substances to neurons. How astrocytes regulate neural functions via altering the neuronal metabolic state remains ...elusive. Here, we demonstrate that astrocytic ApoE vectors a variety of microRNAs (miRNAs), and these miRNAs specifically silence genes involved in neuronal cholesterol biosynthesis, ultimately accounting for accumulation of the pathway-initiating substrate acetyl-CoA. Consequently, histone acetylation is promoted, and transcription is activated in neurons. Functionally, we demonstrate that ApoE-mediated neuronal histone acetylation leads to increased H3K27ac enrichment in the promoters of multiple neuronal immediate early genes and subsequently to enhanced memory consolidation in mice. Importantly, human ApoE4 vectors lower levels of miRNAs than ApoE3 and therefore is less capable of metabolic and epigenetic regulation in neurons. Collectively, our findings define an astrocytic ApoE-mediated neuronal epigenetic mechanism as a novel means through which astrocytes modulate brain connectivity and function.
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•Astrocytic ApoE vectors miRNA species that silence neuronal cholesterol biosynthesis•Astrocytic ApoE promotes acetyl-CoA, histone acetylation, and transcription in neurons•Memory consolidation is potentiated by ApoE-mediated epigenetic control in the brain•ApoE4 is less capable of metabolic and epigenetic regulation in neurons than ApoE3
Li et al. demonstrate that astrocytic ApoE regulates neuronal epigenetic states via reprogramming its lipid metabolism. This ApoE-mediated epigenetic mechanism controls brain function, particularly memory consolidation in mice. Moreover, human ApoE4, a strong risk factor for Alzheimer’s disease, is less capable of metabolic and epigenetic regulation in neurons than ApoE3.
Utilization of N,N‐dimethylformamide (DMF) as an amine source and reductant for synthesizing tertiary amines is a promising way to replace the substrates formaldehyde and dimethylamine, and it is ...desirable to seek porous acid‐resistant catalysts for heterogeneous catalysis of this reaction. Herein, a robust metal–organic framework (MOF) {Th6O4(OH)4(H2O)6(BCP)3⋅10 DMF}n (1) containing stacked nanocages with a diameter of 1.55 nm was constructed. Compound 1 can maintain its single‐crystal structure even kept in air at 400 °C for 3 h, and in DMF or water at 200 °C for 7 days. Density functional theory (DFT) calculations suggested that the high interaction energy between the Th6O4(OH)4(H2O)612+ clusters and ligands was responsible for the excellent stability of 1. Catalytic investigations revealed that 1 can effectively and size‐selectively catalyze the reductive amination of aldehydes with DMF, and it can be reused at least five times without obvious loss in catalytic activity.
A strong‐acid‐resistant Th6 cluster‐based framework containing stacked nanocages was constructed and demonstrated excellent efficiency and stability in the reductive amination of various aldehydes with N,N‐dimethylformamide as the amino source, reductant and solvent. In addition, this catalyst displayed a catalytic size‐selectivity for aldehydes that has not been observed previously for this reaction.
Abstract
The topology concept in the condensed physics and acoustics is introduced into the elastic wave metamaterial plate, which can show the topological property of the flexural wave. The elastic ...wave metamaterial plate consists of the hexagonal array which is connected by the piezoelectric shunting circuits. The Dirac point is found by adjusting the size of the unit cell and numerical simulations are illustrated to show the topological immunity. Then the closing and breaking of the Dirac point can be generated by the negative capacitance circuits. These investigations denote that the topological immunity can be achieved for flexural wave in mechanical metamaterial plate. The experiments with the active control action are finally carried out to support the numerical design.
Glutathione (GSH) in tumors consumes 1O2 and seriously inhibits the PDT effect. MnO2-coated porphyrin metal–organic frameworks are developed to realize the oxidation of GSH by MnO2 for enhanced PDT, ...activated MR imaging, and controllable release of DOX as magnetic resonance imaging guided drug–PDT dual-therapy.
Chemotherapy remains restricted by its toxic adverse effects and resistance to drugs. The treatment of nitric oxide (NO) combined with imaging-guided physical therapy is a promising alternative for ...clinical applications. Herein, we report nanoscale metal–organic framework (NMOF) systems to integrate magnetic resonance (MR) imaging, spatiotemporally controllable NO delivery, and photothermal therapy (PTT) as a new means of cancer theranostics. As a proof of concept, the NMOFs are prepared with biocompatible Zr4+ ions and Mn-porphyrin as a bridging ligand. By inserting paramagnetic Mn ions into porphyrin rings, Mn-porphyrin renders the NMOFs strong T 1-weighted MR contrast capacity and high photothermal conversion for efficient PTT. S-Nitrosothiol (SNO) is conjugated to the surfaces of the NMOFs for heat-sensitive NO generation. Moreover, single near-infrared (NIR) light triggers the controllable NO release and PTT simultaneously for their efficient synergistic therapy with one-step operation. Upon intravenous injection, NMOF–SNO shows effective tumor accumulation as exposed by the MR images of the tumor-bearing mice. When exposed to the NIR laser, the tumors of mice injected with NMOF–SNO are completely inhibited, verifying the efficiency of NMOF–SNO. For the first time, Mn-porphyrin NMOFs are developed to be an effective theranostic system for MR imaging-guided controllable NO release and photothermal synergetic therapy under single NIR irradiation.
Spatial transcriptomics approaches have substantially advanced our capacity to detect the spatial distribution of RNA transcripts in tissues, yet it remains challenging to characterize ...whole-transcriptome-level data for single cells in space. Addressing this need, researchers have developed integration methods to combine spatial transcriptomic data with single-cell RNA-seq data to predict the spatial distribution of undetected transcripts and/or perform cell type deconvolution of spots in histological sections. However, to date, no independent studies have comparatively analyzed these integration methods to benchmark their performance. Here we present benchmarking of 16 integration methods using 45 paired datasets (comprising both spatial transcriptomics and scRNA-seq data) and 32 simulated datasets. We found that Tangram, gimVI, and SpaGE outperformed other integration methods for predicting the spatial distribution of RNA transcripts, whereas Cell2location, SpatialDWLS, and RCTD are the top-performing methods for the cell type deconvolution of spots. We provide a benchmark pipeline to help researchers select optimal integration methods to process their datasets.
Radiographically assisted dental identification is an important means for individual identification. Specific identifiers help to quickly filter some of the possible corresponding AM and PM images at ...the beginning. The study seeks specific oral and maxillofacial identifiers in panoramic radiographs. A total of 920 panoramic radiographs from 460 live patients were used. The most recent radiograph served as the surrogate post‐mortem (PM) record of an unidentified person, and the earliest radiograph served as the ante‐mortem (AM) record of the same person. We evaluated the following four groups of identifiers of the images: (1) dental morphology, tooth number, and position; (2) dental treatment and pathology; (3) morphological identifiers of the jaw; and (4) pathological identifiers of the jaw. The ratio of each identifier being identified simultaneously in the AM and PM databases was determined. Specific identifiers were defined as those that appeared at low frequency (ratio: 0%–0.250%). A total of 18 specific oral and maxillofacial identifiers were determined. The specific identifiers were a retained deciduous tooth (0.011%), S‐shaped deflection of a tooth root (0.012%), distal deflection of tooth root (0.017%), inverted impaction (0.018%), malposition (0.038%), supernumerary teeth (0.061%), mesial deflection of tooth root (0.092%), microdontia (0.136%), buccal/lingual impaction (0.188%), cementoma (0.002%), hypercementosis (0.002%), continuous crown (0.004%), pulp calcification (0.023%), attrition (0.030%), residual root (0.106%), root resorption (0.137%), implant (0.156%), and osteomyelitis (0.002%). Identifiers of the teeth and jaw can be used for human identification, and dental identifiers are more specific than identifiers of jaw.
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