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Covalent organic frameworks (COFs) with a donor‐acceptor (D−A) architecture have been investigated as prospective semiconducting materials, particularly for photocatalytic processes. The incorporation of electron donating and accepting moieties into the COF backbone creates nano heterojunctions, enhancing efficient light absorption, charge separation, and charge transport. Herein, three pyrene‐based COFs were well designed for the aerobic coupling of amines under air atmosphere with blue‐LED irradiation. Among the three COFs, the Py‐Por‐COF with D−A structure exhibits the highest photocatalytic performance and demonstrates a remarkable apparent quantum efficiency of 11.3 % at 420 nm. In addition, the Py‐Por‐COF maintains a good level of crystallinity and high yield even undergone four cycles, showcasing the exceptional potential of D−A structure COFs in the field of photocatalytic organic transformation. [ABSTRACT FROM AUTHOR]

Covalent organic frameworks (COFs) emerge as innovative photocatalysts featuring systematically tuned chemical structures, nano-porosity, and photoelectric properties. We have shown in the last years that COFs are excellent photocatalysts and they are able to produce hydrogen peroxide (H2O2) from oxygen and water. Despite the recent surge in the photosynthesis of H2O2 using COFs, its subsequent application for tandem pollutant remediation as a tangible green alternative to Fenton chemistry has not yet been comprehensively explored. In this study, we synthesized three highly crystalline sp2 COFs with different donor–acceptor (D–A) strengths, employing triazine units as the electron acceptor moiety. The D–A alignment promotes photogenerated charge separation, augmenting the photocatalytic process, which resulted in the TMT-TT-COF achieving a H2O2 production rate of 1952 μmol g−1 h−1 without any sacrificial agents. The COFs also manifested a rapid photocatalytic degradation of bisphenol A (BPA) from a variety of real-life waterbodies. This study pioneers the in situ H2O2 production via COFs to subsequently generate other reactive oxygen species (ROS) for direct organic pollutant degradation in the visible region. [ABSTRACT FROM AUTHOR]

Azo dye residues pollute water, which are difficult to decompose, and posing a major threat to the ecological environment. The residues of Chinese medicine still have many possibilities for use after its medicinal value has been brought into play. In this study, secondary residue biochar activation (Na2CO3‐modified, SBA) and secondary residue biochar (unmodified, SBC) were prepared from the secondary residue of snow lotus at 200–600°C. Surface features were obtained by Brunauer–Emmett–Teller N2 method and combined with scanning electron microscopy, and their structures were analyzed by x‐ray diffraction spectroscopy, Fourier infrared and near‐infrared spectroscopy. The effects of five factors, including initial concentration, contact time and adsorption temperature and so forth, on the adsorption of methyl red (MR) and methyl orange (MO) solutions were investigated. Results showed that the biochar yield, specific surface area, and pore size increased after modification. modification promoted the formation of the internal structure aromatization and oxygen‐containing functional groups. Adsorption experiments showed that the surroundings pH = 8, the dyes adsorption concentration of 8 mg/L, adsorption temperature of 20–40°C and time of about 1 h were more stable. Under the condition, the removal of MO by SBA could reach approximately 60%–80% (480–640 mg/g), while the removal of MR could reach more than 90% (>720 mg/g).The charcoal prepared and modified under high temperature conditions was more effective for MO adsorption, while MR relied on low temperature effectively. This study provides a new choice of adsorbent for MR and MO and finds a new direction for the utilization of snow lotus residues. [ABSTRACT FROM AUTHOR]

Summary: In the article, we devise streaming algorithms for maximization of a monotone submodular function subject to a cardinality constraint on the integer lattice. Based on the observation that lattice submodularity is not equivalent to diminishing return submodularity on the integer lattice but rather a weaker condition, we propose a one‐pass streaming algorithm with a modified binary search as subroutine of each step. Finally, we show that the algorithm is with approximation ratio 1/2−ε, memory complexity O(ε−1klogk), and per‐element query complexity O(ε−2log2k). [ABSTRACT FROM AUTHOR]

The photocatalytic oxygen reduction reaction (ORR) towards hydrogen peroxide (H2O2) is a promising but challenging alternative to the industrial anthraquinone process. Crystalline porous covalent organic frameworks (COFs), a new generation of semiconductors, have attracted significant attention because they exhibit broad visible-light harvesting, possess tunable energy levels, and facilitate facile separation and migration of photogenerated charge pairs. The modulation of the energy levels of COFs could facilitate charge transport, resulting in better photocatalytic performance. Herein, the π-conjugation system of COFs was extended via a post-sulfurization process, leading to a considerably enhanced photocatalytic activity. During the sulfurization process, imine-linked COFs were converted into thiazole-linked COFs to extend the conjugation structure of COFs in the x and y directions, resulting in higher transport of electrons. The thiazole-linked 4PE-N-S presents the best photocatalytic H2O2 generation performance with a rate of 1574 μmol g−1 h−1, which is about 5.8 and 3.7 times higher than that of imine-linked 4PE-N and 4PE-TT, respectively. Our findings provide new prospects for the design and synthesis of highly active organic photocatalysts for solar-to-chemical energy conversion. [ABSTRACT FROM AUTHOR]