As a new generation of porous materials, porous organic polymers (POPs), have recently emerged as a powerful platform of heterogeneous photocatalysis. POPs are constructed using extensive organic ...synthesis methodologies, with various functional organic units being connected
via
high-energy covalent bonds. This review systematically presents the recent advances in POPs for visible-light driven organic transformations. Herein, we firstly summarize the common construction strategies for POP-based photocatalysts based on two major approaches: pre-design and post-modification; secondly, we categorize and summarize the synthesis methods and organic reaction types for constructing various types of POPs. We then classify and introduce the specific reactions of current light-driven POP-mediated organic transformations. Finally, we outline the current state of development and the problems faced in light-driven organic transformations by POPs, and we present some perspectives to motivate the reader to explore solutions to these problems and confront the present challenges in the development process.
Porous organic polymers (POPs), with their high specific surface area, low density, good stability, uniform pore size, structural versatility, and designability, have recently emerged as a powerful platform of heterogeneous photocatalysis.
Covalent organic frameworks (COFs), connecting different organic units into one system through covalent bonds, are crystalline organic porous materials with 2D or 3D networks. Compared with ...conventional porous materials such as inorganic zeolite, active carbon, and metal‐organic frameworks, COFs are a new type of porous materials with well‐designed pore structure, high surface area, outstanding stability, and easy functionalization at the molecular level, which have attracted extensive attention in various fields, such as energy storage, gas separation, sensing, photoluminescence, proton conduction, magnetic properties, drug delivery, and heterogeneous catalysis. Herein, the recent advances in metal‐free COFs as a versatile platform for heterogeneous catalysis in a wide range of chemical reactions are presented and the synthetic strategy and promising catalytic applications of COF‐based catalysts (including photocatalysis) are summarized. According to the types of catalytic reactions, this review is divided into the following five parts for discussion: achiral organic catalysis, chiral organic conversion, photocatalytic organic reactions, photocatalytic energy conversion (including water splitting and the reduction of carbon dioxide), and photocatalytic pollutant degradation. Furthermore, the remaining challenges and prospects of COFs as heterogeneous catalysts are also presented.
Covalent organic frameworks (COFs) as a new type of organic porous materials have aroused great interest in the field of heterogeneous catalysis. Herein, the applications of metal‐free COFs in organic catalysis, photocatalysis, energy conversion, and pollutant degradation are systematically summarized. In addition, the main challenges in this area and the potential prospects for future work are also discussed.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
A filtering algorithm based on frequency domain spline type, frequency domain spline adaptive filters (FDSAF), effectively reducing the computational complexity of the filter. However, the FDSAF ...algorithm is unable to suppress non-Gaussian impulsive noises. To suppression non-Gaussian impulsive noises along with having comparable operation time, a maximum correntropy criterion (MCC) based frequency domain spline adaptive filter called frequency domain maximum correntropy criterion spline adaptive filter (FDSAF-MCC) is developed in this paper. Further, the bound on learning rate for convergence of the proposed algorithm is also studied. And through experimental simulations verify the effectiveness of the proposed algorithm in suppressing non-Gaussian impulsive noises. Compared with the existing frequency domain spline adaptive filter, the proposed algorithm has better performance.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
A azine‐linked covalent organic framework, COF‐JLU2, was designed and synthesized by condensation of hydrazine hydrate and 1,3,5‐triformylphloroglucinol under solvothermal conditions for the first ...time. The new covalent organic framework material combines permanent micropores, high crystallinity, good thermal and chemical stability, and abundant heteroatom activated sites in the skeleton. COF‐JLU2 possesses a moderate BET surface area of over 410 m2 g−1 with a pore volume of 0.56 cm3 g−1. Specifically, COF‐JLU2 displays remarkable carbon dioxide uptake (up to 217 mg g−1) and methane uptake (38 mg g−1) at 273 K and 1 bar, as well as high CO2/N2 (77) selectivity. Furthermore, we further highlight that it exhibits a higher hydrogen storage capacity (16 mg g−1) than those of reported COFs at 77 K and 1 bar.
An azine‐linked covalent organic framework was constructed by condensation of hydrazine hydrate and 1,3,5‐triformylphloroglucinol under solvothermal conditions. While the framework possesses moderate surface areas, it exhibits excellent capture and uptake capacities for CO2 (217 mg g−1), H2 (16 mg g−1), and CH4 (38 mg g−1) at 1 bar pressure, with high adsorption selectivity for CO2 over N2.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
The cycloaddition of CO2 to epoxides to form cyclic carbonates is very promising and does not generate any side products. Metal-free, heterogeneous organocatalysts offer an environmentally friendly ...alternative to traditional metal-based catalysts. Herein two triazine-based covalent organic frameworks (COF-JLU6 and COF-JLU7) were successfully synthesized under solvothermal conditions. The structural and chemical properties of COFs were fully characterized by using powder X-ray diffraction analysis, structural simulation, Fourier transform infrared spectroscopy, 13C solid-state NMR spectroscopy, electron microscopy, thermogravimetric analysis and nitrogen adsorption. The two COF materials combine mesopores, high crystallinity and good stability, as well as a large number of hydroxy groups in the pore walls. They possess a high Brunauer–Emmett–Teller (BET) specific surface area up to 1390 m2 g−1 and a large pore volume of 1.78 cm3 g−1. The COF-JLU7 displays a high CO2 uptake of 151 mg g−1 at 273 K and 1 bar. Importantly, COF-JLU7 was found to be a highly effective catalyst to convert CO2 into cyclic carbonate through the cycloaddition reaction with epoxides under mild conditions. The effect of reaction parameters, such as reaction temperature, reaction time and CO2 pressure, on the catalytic performance was also investigated in detail. Moreover, the new framework-based catalyst can be recovered and reused five times without a significant loss of catalytic efficiency.
In this paper, a generalized maximum Versoria criterion algorithm (GMVC) based on wiener spline adaptive filter, called SAF–GMVC, is proposed. The proposed algorithm is used for nonlinear system ...identification under non-Gaussian environment. To improve the convergence performance of the SAF–GMVC, the momentum stochastic gradient descent (MSGD) is introduced. In order to further reduce the steady-state error, the variable step-size algorithm is introduced, called as SAF–GMVC–VMSGD. Simulation results demonstrate that SAF–GMVC–VMSGD achieves better filtering effective against non-Gaussian noise.
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EMUNI, FIS, FZAB, GEOZS, GIS, IJS, IMTLJ, KILJ, KISLJ, MFDPS, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, SBMB, SBNM, UKNU, UL, UM, UPUK, VKSCE, ZAGLJ
Abstract
Aqueous organic redox flow batteries (AORFBs) are a promising technology for large-scale electricity energy storage to realize efficient utilization of intermittent renewable energy. In ...particular, organic molecules are a class of metal-free compounds that consist of earth-abundant elements with good synthetic tunability, electrochemical reversibility and reaction rates. However, the short cycle lifetime and low capacity of AORFBs act as stumbling blocks for their practical deployment. To circumvent these issues, here, we report molecular engineered dihydroxyanthraquinone (DHAQ)-based alkaline electrolytes. Via computational studies and operando measurements, we initially demonstrate the presence of a hydrogen bond-mediated degradation mechanism of DHAQ molecules during electrochemical reactions. Afterwards, we apply a molecular engineering strategy based on redox-active polymers to develop capacity-boosting composite electrolytes. Indeed, by coupling a 1,5-DHAQ/poly(anthraquinonyl sulfide)/carbon black anolyte and a Fe(CN)
6
3−/4−
alkaline catholyte, we report an AORFB capable of delivering a stable cell discharge capacity of about 573 mAh at 20 mA/cm
2
after 1100 h of cycling and an average cell discharge voltage of about 0.89 V at the same current density.
Geometric algebra (GA) is an efficient tool to deal with hypercomplex processes due to its special data structure. In this article, we introduce the affine projection algorithm (APA) in the GA domain ...to provide fast convergence against hypercomplex colored signals. Following the principle of minimal disturbance and the orthogonal affine subspace theory, we formulate the criterion of designing the GA-APA as a constrained optimization problem, which can be solved by the method of Lagrange Multipliers. Then, the differentiation of the cost function is calculated using geometric calculus (the extension of GA to include differentiation) to get the update formula of the GA-APA. The stability of the algorithm is analyzed based on the mean-square deviation. To avoid ill-posed problems, the regularized GA-APA is also given in the following. The simulation results show that the proposed adaptive filters, in comparison with existing methods, achieve a better convergence performance under the condition of colored input signals.
Two-dimensional covalent organic frameworks (2D-COFs) are excellent candidates for photocatalytic organic transformations due to their periodic columnar π-arrays and ordered nanochannels. Here, we ...present a novel 2D-COF that features permanent porosity with high surface area and large pore volume, and exhibits a high crystallinity and an excellent stability. Indeed, the new 2D-COF was found to be a highly efficient, metal-free, recyclable heterogeneous photocatalyst for oxidative C–H functionalizations under visible-light irradiation using O
2
as a green oxygen source.
Metal-free, visible-light active and heterogeneous organic photocatalysts offer a more sustainable and environmentally friendly alternative to traditional metal-based catalysts. Here a porous organic ...hyper-crosslinked polymer, CF-HCP, was successfully synthesized through a facile and cost-effective process. The chemical and structural properties of CF-HCP were fully characterized by using powder X-ray diffraction analysis, Fourier transform infrared spectroscopy, 13C solid-state NMR spectroscopy, electron microscopy, thermogravimetric analysis, X-ray photoelectron spectroscopy and nitrogen adsorption. The new three-dimensional hyper-crosslinked network possesses a high Brunauer-Emmett-Teller (BET) specific surface area up to 1200 m2 g-1 with a pore volume of 0.92 cm3 g-1, and exhibits good thermal, chemical and photochemical stability. Importantly, CF-HCP was found to be a highly effective heterogeneous photocatalyst for a wide range of organic reactions, including the oxidative coupling of primary amines, dehydrogenation of nonactive secondary amine substrates, and selective oxidation of sulfide under visible-light irradiation and using molecular oxygen as a clean oxidant. In particular, mild reaction conditions, ease of product separation by simple filtration, significant recyclability and low cost make this network material an economical and eco-friendly catalyst for the preparation of versatile organic compounds.
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