Great attention has been given to metal–organic frameworks (MOFs)-derived solid bases because of their attractive structure and catalytic performance in various organic reactions. The extraordinary ...skeleton structure of MOFs provides many possibilities for incorporation of diverse basic functionalities, which is unachievable for conventional solid bases. The past decade has witnessed remarkable advances in this vibrant research area; however, MOFs for heterogeneous basic catalysis have never been reviewed until now. Therefore, a review summarizing MOFs-derived base catalysts is highly expected. In this review, we present an overview of the recent progress in MOFs-derived solid bases covering preparation, characterization, and catalytic applications. In the preparation section, the solid bases are divided into two categories, namely, MOFs with intrinsic basicity and MOFs with modified basicity. The basicity can originate from either metal sites or organic ligands. Different approaches used for generation of basic sites are included, and each approach is described with representative examples. The fundamental principles for the design and fabrication of MOFs with basic functionalities are featured. In the characterization section, experimental techniques and theoretical calculations employed for characterization of basic MOFs are summarized. Some representive experimental techniques, such as temperature-programmed desorption of CO2 (CO2-TPD) and infrared (IR) spectra of different probing molecules, are covered. Following preparation and characterization, the catalytic applications of MOFs-derived solid bases are dealt with. These solid bases have potential to catalyze some well-known “base-catalyzed reactions” like Knoevenagel condensation, aldol condensation, and Michael addition. Meanwhile, in contrast to conventional solid bases, MOFs show some different catalytic properties due to their special structural and surface properties. Remarkably, characteristic features of MOFs-derived solid bases are described by comparing with conventional inorganic counterparts, keeping in mind the current opportunities and challenges in this field.
In recent years, feature selection for multilabel classification has attracted attention in machine learning and data mining. However, some feature selection methods ignore the correlations among ...labels, resulting in low performance, and most of them face challenges in determining an appropriate neighborhood radius for neighborhood systems and suffer from expensive time cost. To overcome the issues, we propose a novel feature selection method using Fisher score and multilabel neighborhood rough sets (MNRS) in multilabel neighborhood decision systems. First, to identify the correlations between labels under a binary distribution, two types of new mutual information between labels are considered, and their balance coefficients are defined. By enhancing strong correlations and weakening weak correlations between labels, a mutual information-based Fisher score model with a second-order correlation between labels is designed to fit multilabel data. Second, to address the problem of automatically choosing a neighborhood radius, a subset of heterogeneous and homogeneous samples is employed to develop a new classification margin as a neighborhood radius, and some concepts of neighborhood, neighborhood class, and upper and lower approximations are formulated for multilabel neighborhood decision systems. The weight and dependency degree are presented to effectively measure the uncertainty of samples in multilabel neighborhood decision systems. Thus, we further present a new classification margin-based MNRS model. Finally, a filter-wrapper preprocessing algorithm for feature selection using the improved Fisher score model is proposed to decrease the spatiotemporal complexity of multilabel data, and a heuristic feature selection algorithm is designed for improve classification performance on multilabel datasets. Experimental results on thirteen multilabel datasets show that the proposed algorithm is effective in selecting significant features, demonstrating its excellent classification ability in multilabel datasets.
Photoresponsive metal–organic frameworks (PMOFs) are of interest for tailorable CO2 adsorption. However, modulation of CO2 adsorption on PMOFs is based on steric hindrance or structural change owing ...to weak interactions between CO2 and active sites. It is challenging to fabricate PMOFs with strong but tailorable sites for CO2 adsorption. Now, the construction of PMOFs with target‐specific (strong) active sites is achieved by introducing tetraethylenepentamine into azobenzene‐functionalized MOFs for tailorable CO2 adsorption. Amines are specific active sites for CO2, contributing to capture CO2 selectively. Cis/trans isomerization of azobenzene motifs trigged by UV/Vis light adjusts the electrostatic potential of amines significantly, leading to exposure/shelter of amines and modulation of CO2 adsorption on strong active sites. This system enables us to design adsorption processes for CO2 capture from mixtures, which is impossible to realize by traditional PMOFs.
Smart adsorbents were fabricated by introducing target‐specific active sites (amines) into photoresponsive metal–organic frameworks (PMOFs). The cis/trans isomerization of azobenzene motifs trigged by UV/Vis light irradiation adjusts the electrostatic potential of amines significantly. This leads to exposure/shelter of amines and successful modulation of CO2 adsorption on strong active sites, which is impossible to realize by traditional PMOFs.
High‐performance uncooled photodetectors operating in the long‐wavelength infrared and terahertz regimes are highly demanded in the military and civilian fields. Photothermoelectric (PTE) detectors, ...which combine photothermal and thermoelectric conversion processes, can realize ultra‐broadband photodetection without the requirement of a cooling unit and external bias. In the last few decades, the responsivity and speed of PTE‐based photodetectors have made impressive progress with the discovery of novel thermoelectric materials and the development of nanophotonics. In particular, by introducing hot‐carrier transport into low‐dimensional material–based PTE detectors, the response time has been successfully pushed down to the picosecond level. Furthermore, with the assistance of surface plasmon, antenna, and phonon absorption, the responsivity of PTE detectors can be significantly enhanced. Beyond the photodetection, PTE effect can also be utilized to probe exotic physical phenomena in spintronics and valleytronics. Herein, recent advances in PTE detectors are summarized, and some potential strategies to further improve the performance are proposed.
The room‐temperature detection of long‐wavelength infrared and terahertz radiation can be realized by photothermoelectric (PTE) detectors. The responsivity and the response speed of PTE‐based photodetectors have made impressive progress with the discovery of novel thermoelectric materials and the development of nanophotonics. Beyond light detection, the PTE effect can be utilized to study novel physical phenomena in spintronics and valleytronics.
Fully integrated ultrathin, transparent and foldable energy storage devices are essential for the development of smart wearable electronics, yet typical supercapacitor electrodes are ...substrate-supported which limits their thickness, transparency and mechanical properties. Employing freestanding transparent electrodes with no substrate support could bring ultrathin, foldable and designable supercapacitors closer to reality. Herein, we report a freestanding, ultrathin (<5 μm), highly conductive (3 × 10 4 S cm −1 ), highly transparent (>84% transmittance) and foldable metallic network electrode, loaded with MnO 2 by electrochemical deposition, as a supercapacitor electrode. The freestanding metallic network electrode is fabricated via a simple and low-cost laser direct-writing micro-patterning technique followed by a selective electrodeposition process, where the metallic network patterns, network periods, metal thickness and also the electrode film patterns can be designed for different applications. The obtained freestanding MnO 2 @Ni network electrode delivers an outstanding areal capacitance of 80.7 mF cm −2 and long-term performance stability (96.3% after 10 000 cycles). Moreover, the symmetric solid-state supercapacitors employing the freestanding MnO 2 @Ni network electrode not only show high areal capacitance as well as high optical transparency (>80% transmittance), but also can be tailored, attached, folded, rolled up, and crumpled into any object or various shapes with only slight performance degradation. The advent of such freestanding transparent metallic network electrodes may open up a new avenue for realizing fully integrated ultrathin, foldable and designable supercapacitors towards self-powered wearable electronics.
Mesoporous solid bases are extremely desirable in green catalytic processes, due to their advantages of accelerated mass transport, negligible corrosion, and easy separation. Great progress has been ...made in mesoporous solid bases in the last decade. In addition to their wide applications in the catalytic synthesis of organics and fine chemicals, mesoporous solid bases have also been used in the field of energy and environmental catalysis. Development of mesoporous solid bases is therefore of significant importance from both academic and practical points of view. In this review, we provide an overview of the recent advances in mesoporous solid bases, which is basically grouped by the support type and each category is illustrated with typical examples. Cooperative catalysts derived from the incorporation of additional functionalities (
i.e.
acid and metal) into mesoporous solid bases are also included. The fundamental principles of how to design and fabricate basic materials with mesostructure are highlighted. The mechanism of the formation of basic sites in different mesoporous systems is discussed as well.
Recent advances in mesoporous solid bases were reviewed, and fundamental principles of how to fabricate efficient basic catalysts were highlighted.
For heterogeneous data sets containing numerical and symbolic feature values, feature selection based on fuzzy neighborhood multigranulation rough sets (FNMRS) is a very significant step to ...preprocess data and improve its classification performance. This article presents an FNMRS-based feature selection approach in neighborhood decision systems. First, some concepts of fuzzy neighborhood rough sets and neighborhood multigranulation rough sets are given, and then the FNMRS model is investigated to construct uncertainty measures. Second, the optimistic and pessimistic FNMRS models are built by using fuzzy neighborhood multigranulation lower and upper approximations from algebra view, and some fuzzy neighborhood entropy-based uncertainty measures are developed in information view. Inspired by both algebra and information views based on the FNMRS model, the fuzzy neighborhood pessimistic multigranulation entropy is proposed. Third, the Fisher score model is utilized to delete irrelevant features to decrease the complexity of high-dimensional data sets, and then, a forward feature selection algorithm is provided to promote the performance of heterogeneous data classification. Experimental results on 12 data sets show that the presented model is effective for selecting important features with the higher stability of classification in neighborhood decision systems.
The rediscovery of black phosphorus (BP) has expanded the 2D family into Group 15 (Nitrogen Group) elements, among which bismuthene is the latest member with extraordinary opto-electronic, catalytic ...and biocompatible properties and potential as a 2D topological insulator. However, bulk Bi is not easily mechanically exfoliated as its counterpart of BP. Thus, to date, the reports on 2D Bi fabrication are rare, and investigations on its nonlinear optical properties are even less. Herein, we rationally designed a new strategy combining acid-interaction and liquid exfoliation to successfully transform metal bulk Bi into few-layer semiconductor, which resulted in unseen opto-electronic properties, such as tunable nonlinear responses all the way to the near-infrared (NIR) region. This band is critical for telecommunication and military purposes, but currently, functioning materials are extremely scarce. The origin of this strong saturable absorption was thoroughly explored through time-resolved spectroscopy spanning from the fs to μs timescale, which indicated ultrafast fs to ps carrier dynamics in the early stage and long exciton bleaching recovery up to μs. As a proof-of-concept application, the as-prepared 2D Bi was employed as a saturable absorber to mode-lock a Tm-doped fiber laser and successfully realized a 2 μm NIR-wavelength output. This study not only offers an effective and scalable method to fabricate the new 2D family member bismuthene with extraordinary stability, but also explores its strong and broad nonlinear responses extending into the NIR region and fundamental photoinduced dynamics, which demonstrate the full potential of 2D Bi for application in opto-electronic devices and nonlinear optics.
Abstract
The zeolite Cu(I)Y is promising for adsorptive removal of thiophenic sulfur compounds from transportation fuels. However, its application is seriously hindered by the instability of Cu(I), ...which is easily oxidized to Cu(II) even under atmospheric environment due to the coexistence of moisture and oxygen. Here, we report the adjustment of zeolite microenvironment from hydrophilic to superhydrophobic status by coating polydimethylsiloxane (yielding Cu(I)Y@P), which isolates moisture entering the pores and subsequently stabilizes Cu(I) despite the presence of oxygen. Cu(I) in Cu(I)Y@P is stable upon exposure to humid atmosphere for 6 months, while almost all Cu(I) is oxidized to Cu(II) in Cu(I)Y for only 2 weeks. The optimized Cu(I)Y@P material after moisture exposure can remove 532 μmol g
−1
of thiophene and is much superior to Cu(I)Y (116 μmol g
−1
), regardless of similar uptakes for unexposed adsorbents. Remarkably, Cu(I)Y@P shows excellent adsorption capacity of desulfurization for water-containing model fuel.
Dihydromyricetin (DMY), one of the flavonoids in vine tea, exerts several pharmacological actions. However, it is not clear whether DMY has a protective effect on pressure overload-induced myocardial ...hypertrophy. In the present study, male C57BL/6 mice aging 8⁻10 weeks were subjected to transverse aortic constriction (TAC) surgery after 2 weeks of DMY (250 mg/kg/day) intragastric administration. DMY was given for another 2 weeks after surgery. Blood pressure, myocardial structure, cardiomyocyte cross-sectional area, cardiac function, and cardiac index were observed. The level of oxidative stress in the myocardium was assessed with dihydroethidium staining. Our results showed that DMY had no significant effect on the blood pressure. DMY decreased inter ventricular septum and left ventricular posterior wall thickness, relative wall thickness, cardiomyocyte cross-sectional areas, as well as cardiac index after TAC. DMY pretreatment also significantly reduced arterial natriuretic peptide (ANP), brain natriuretic peptide (BNP) mRNA and protein expressions, decreased reactive oxygen species production and malondialdehyde (MDA) level, while increased total antioxidant capacity (T-AOC), activity of superoxide dismutase (SOD), expression of sirtuin 3 (SIRT3), forkhead-box-protein 3a (FOXO3a) and SOD2, and SIRT3 activity in the myocardium of mice after TAC. Taken together, DMY ameliorated TAC induced myocardial hypertrophy in mice related to oxidative stress inhibition and SIRT3 pathway enhancement.
PDF
