Dynamic Cleavage-Remodeling of Covalent Organic Networks into Multidimensional Superstructures.

Superstructures with complex hierarchical spatial configurations exhibit broader structural depth than single hierarchical structures and the associated broader application prospects. However, current preparation methods are greatly constrained by cumbersome steps and harsh conditions. Here, for the first time, a concise and efficient thermally responsive dynamic synthesis strategy for the preparation of multidimensional complex superstructures within soluble covalent organic networks (SCONs) with tunable morphology from 0D hollow supraparticles to 2D films is presented.

Constructing ordered and tunable extrinsic porosity in covalent organic frameworks via water-mediated soft-template strategy.

As one of the most attractive methods for the synthesis of ordered hierarchically porous crystalline materials, the soft-template method has not appeared in covalent organic frameworks (COFs) due to the incompatibility of surfactant self-assembly and guided crystallization process of COF precursors in the organic phase. Herein, we connect the soft templates to the COF backbone through ionic bonds, avoiding their crystallization incompatibilities, thus introducing an additional ordered arrangement of soft templates into the anionic microporous COFs. The ion exchange method is used to remove the templates while maintaining the high crystallinity of COFs, resulting in the construction of COFs with ordered hierarchically micropores/mesopores, herein named OHMMCOFs (OHMMCOF-1 and OHMMCOF-2).

A methodology to prioritize ecosystem restoration of in-situ well pads in the Permian Basin of western Texas and southeastern New Mexico, USA.

Since the mid-2000s, drilling and production of oil and gas activities have grown exponentially in the southwestern United States. The clearing of pre-existing vegetation and topsoil to build well pads is known to have a broad range of ecological, biological, hydrological, and health impacts, therefore ecosystem restoration of the well pads is generally required. This process, however, is often complicated by limited funding, various governing bodies and ownership, and frequent extreme weather events.

Simple and Efficient Hydrogen Bond-Assisted Unit Exchange for Constructing Highly Soluble Covalent Organic Frameworks.

The majority of COFs synthesized using current methods exist as insoluble powders, which is unfavorable for processing and molding and greatly limits their practical applications. The syntheses of solution-processable or soluble COFs are challenging but hold immense promise and potential. Herein, for the first time, we have developed a simple and high-efficiency solvothermal-treated unit exchange approach to convert insoluble COF powders into smaller, highly soluble COFs via a hydrogen bond-assisted strategy.

Regioselective One-Step Cyclization and Aromatization towards Directly Amino-Functionalized Covalent Organic Framework with Stable Benzodiimidazole Linkage.

The compatibility of crystallinity, stability, and functionality in covalent organic frameworks (COFs) is challenging but significant in reticular chemistry and materials science. Herein, it is presented for the first time a strategy to synthesize directly amino-functionalized COF with stable benzodiimidazole linkage by regioselective one-step cyclization and aromatization. Bandrowski's base with two types of amino groups is used as a unique monomer, providing not only construction sites for the material framework through specific region-selective reaction, but also amino active sites for functionality, which is usually difficult to achieve directly in COF synthesis because amino groups are the participants in COF bonding.

Perspectives on Medical Education in an Increasingly Globalized Society: Recognizing and Embracing Our Diversity.

Medical curricula around the globe are diverse, accommodating the social, political, cultural, and health needs in each country. Every medical school has the responsibility to educate graduates capable of providing quality medical care to their communities. Yet true globalization of medical education is a challenge.

Monomer Symmetry-Regulated Defect Engineering: In Situ Preparation of Functionalized Covalent Organic Frameworks for Highly Efficient Capture and Separation of Carbon Dioxide.

Developing crystalline porous materials with highly efficient CO selective adsorption capacity is one of the key challenges to carbon capture and storage (CCS). In current studies, much more attention has been paid to the crystalline and porous properties of crystalline porous materials for CCS, while the defects, which are unavoidable and ubiquitous, are relatively neglected. Herein, for the first time, we propose a monomer-symmetry regulation strategy for directional defect release to achieve in situ functionalization of COFs while exposing uniformly distributed defect-aldehyde groups as functionalization sites for selective CO capture.

Seasonal variation and provenance of organic matter in the surface sediments of the three gorges reservoir: Stable isotope analysis and implications for agricultural management.

The construction of the Three Gorges Dam has altered the hydrology and increased the trapping of sediment in the reservoir. This has also changed the composition and export of particulate organic matter in the Yangtze River. To understand the seasonal variations and sources of organic matter in sediments, total organic carbon (TOC), total nitrogen (TN), δC and δN in surface sediment samples from the mainstream and tributaries of the Three Gorges Reservoir were measured in the summer (July) and winter (December) of 2017, respectively.

Fully-exposed Pt-Fe cluster for efficient preferential oxidation of CO towards hydrogen purification.

Hydrogen is increasingly being discussed as clean energy for the goal of net-zero carbon emissions, applied in the proton-exchange-membrane fuel cells (PEMFC). The preferential oxidation of CO (PROX) in hydrogen is a promising solution for hydrogen purification to avoid catalysts from being poisoned by the trace amount of CO in hydrogen-rich fuel gas. Here, we report the fabrication of a novel bimetallic Pt-Fe catalyst with ultralow metal loading, in which fully-exposed Pt clusters bonded with neighbor atomically dispersed Fe atoms on the defective graphene surface.

A Magnetically Separable Pd Single-Atom Catalyst for Efficient Selective Hydrogenation of Phenylacetylene.

Selective hydrogenation of alkynes to alkenes plays a crucial role in the synthesis of fine chemicals. However, how to achieve high selectivity and effective separation of the catalyst and substrate while obtaining high activity is the key for this reaction. In this work, a Pd single-atom catalyst is anchored to the shell of magnetic core-shell particles that consist of a Ni-nanoparticles core and a graphene sheets shell (Ni@G) for semi-hydrogenation of phenylacetylene, delivering 93% selectivity to styrene at full conversion with a robust turnover frequency of 7074 h under mild reaction conditions (303 K, 2 bar H ).

Few-Atom Pt Ensembles Enable Efficient Catalytic Cyclohexane Dehydrogenation for Hydrogen Production.

Identification of catalytic active sites is pivotal in the design of highly effective heterogeneous metal catalysts, especially for structure-sensitive reactions. Downsizing the dimension of the metal species on the catalyst increases the dispersion, which is maximized when the metal exists as single atoms, namely, single-atom catalysts (SACs). SACs have been reported to be efficient for various catalytic reactions.

Atomically dispersed metal catalysts on nanodiamond and its derivatives: synthesis and catalytic application.

Atomically dispersed metal catalysts (ADMCs) have attracted increasing interest in the field of heterogeneous catalysis. As sub-nanometric catalysts, ADMCs have exhibited remarkable catalytic performance in many reactions. ADMCs are classified into two categories: single atom catalysts (SACs) and atomically dispersed clusters with a few atoms.

Regulating coordination number in atomically dispersed Pt species on defect-rich graphene for n-butane dehydrogenation reaction.

Metal nanoparticle (NP), cluster and isolated metal atom (or single atom, SA) exhibit different catalytic performance in heterogeneous catalysis originating from their distinct nanostructures. To maximize atom efficiency and boost activity for catalysis, the construction of structure-performance relationship provides an effective way at the atomic level. Here, we successfully fabricate fully exposed Pt clusters on the defective nanodiamond@graphene (ND@G) by the assistance of atomically dispersed Sn promoters, and correlated the n-butane direct dehydrogenation (DDH) activity with the average coordination number (CN) of Pt-Pt bond in Pt NP, Pt cluster and Pt SA for fundamentally understanding structure (especially the sub-nano structure) effects on n-butane DDH reaction at the atomic level.

Pore Size Control Multiple-Site Alkylation to Homogenize Sub-Nanoporous Covalent Organic Frameworks for Efficient Sieving of Xenon/Krypton.

Among various fission products generated in nuclear reactors, xenon and krypton are two important fission gases with high flow, diffusivity, and radioactivity. Moreover, xenon isolated from these products is an expensive industrial resource with wide applications in medicine and lighting, which makes the development of efficient methods for separation of xenon/krypton significant. However, it is usually difficult for xenon/krypton to be adsorbed by chemical adsorbents due to their inert gas properties, and sub-nanoporous adsorbents proven to be workable for the separation of xenon/krypton are still hard to prepare and regulate the pore size.

Construction of covalent organic framework with unique double-ring pore for size-matching adsorption of uranium.

The separation and recovery of key nuclides such as uranium and plutonium from effluents related to nuclear industry is of great significance for alleviating the shortage of nuclear energy resources and protecting the environment and human health. However, the high temperature, strong acidity and radioactivity of the nuclear effluents pose a severe challenge to the separation materials used in such conditions. The diversity of structure, flexibility of design, and excellent physicochemical stability of covalent organic framework materials (COFs) provide the possibility for the directional design and preparation of adsorbents for use under harsh conditions.

A fully conjugated organic polymer via Knoevenagel condensation for fast separation of uranium.

Design and preparation of a kind of pore-free adsorbent with abundant active sites is favorable for fast separation of uranium. Here, a two-dimensional olefin-linked conjugated organic polymer was prepared via the Knoevenagel condensation reaction. The product owns good stability and excellent fluorescence property due to the fully conjugated skeleton.

Redox-Active Two-Dimensional Covalent Organic Frameworks (COFs) for Selective Reductive Separation of Valence-Variable, Redox-Sensitive and Long-Lived Radionuclides.

We report the first example of 2D covalent organic framework nanosheets (Redox-COF1) for the selective reduction and in situ loading of valence-variable, redox-sensitive and long-lived radionuclides (abbreviated as VRL nuclides). Compared with sorbents based on chemical adsorption and physical adsorption, the redox adsorption mechanism of Redox-COF1 can effectively reduce the impact of functional group protonation under the usual high-acidity conditions in chemisorption, and raise the adsorption efficiency from the monotonous capture by pores in physisorption. The adsorption selectivity for UO reaches up to unprecedented ca.

Low Temperature Oxidation of Ethane to Oxygenates by Oxygen over Iridium-Cluster Catalysts.

Direct selective oxidation of light alkanes, such as ethane, into value-added chemical products under mild reaction conditions remains a challenge in both industry and academia. Herein, the iridium cluster and atomically dispersed iridium catalysts have been successfully fabricated using nanodiamond as support. The obtained iridium cluster catalyst shows remarkable performance for selective oxidation of ethane under oxygen at 100 °C, with an initial activity as high as 7.

Anchoring Cu species over nanodiamond-graphene for semi-hydrogenation of acetylene.

The design of cheap, non-toxic, and earth-abundant transition metal catalysts for selective hydrogenation of alkynes remains a challenge in both industry and academia. Here, we report a new atomically dispersed copper (Cu) catalyst supported on a defective nanodiamond-graphene (ND@G), which exhibits excellent catalytic performance for the selective conversion of acetylene to ethylene, i.e.

Atomically Dispersed Pd on Nanodiamond/Graphene Hybrid for Selective Hydrogenation of Acetylene.

We reported here a strategy to use a defective nanodiamond-graphene (ND@G) to prepare an atomically dispersed metal catalyst, i.e., in the current case atomically dispersed palladium catalyst which is used for selective hydrogenation of acetylene in the presence of abundant ethylene.

Pt NPs immobilized on a N-doped graphene@AlO hybrid support as robust catalysts for low temperature CO oxidation.

Platinum nanoparticles (Pt NPs) immobilized on a N-doped graphene@Al2O3 hybrid support (Al2O3@CNx) were synthesized and employed for low temperature CO oxidation. The superior catalytic activity was attributed to a strong metal-support interaction between Pt NPs and the N-doped graphene surface which was also confirmed in the direct dehydrogenation reaction.

An Efficient Metal-Free Catalyst for Oxidative Dehydrogenation Reaction: Activated Carbon Decorated with Few-Layer Graphene.

Activated carbon (AC) has been widely used in the catalysis field because of its low cost, scalable production, high specific surface area, and abundant exposed edge. Because of the amorphous structure, traditional AC is unstable in presence of O at high temperature, which hinders the application of AC catalysts in oxidative dehydrogenation (ODH) of alkanes. Here, partially graphitic AC decorated with few-layer graphene is facilely fabricated by simple high-temperature calcination.