Search

Preorganization is a basic design principle used by nature that allows for synergistic pathways to be expressed. Herein, a full account of the conceptual and experimental development from randomly distributed functionalities to a convergent arrangement that facilitates cooperative binding is given, thus conferring exceptional affinity toward the analyte of interest. The resulting material with chelating groups populated adjacently in a spatially locked manner displays up to two orders of magnitude improvement compared to a random and isolated manner using uranium sequestration as a model application. This adsorbent shows exceptional extraction efficiencies, capable of reducing the uranium concentration from 5 ppm to less than 1 ppb within 10 min, even though the system is permeated with high concentrations of competing ions. The efficiency is further supported by its ability to extract uranium from seawater with an uptake capability of 5.01 mg g−1, placing it among the highest‐capacity seawater uranium extraction materials described to date. The concept presented here uncovers a new paradigm in the design of efficient sorbent materials by manipulating the spatial distribution to amplify the cooperation of functions. [ABSTRACT FROM AUTHOR]

Abstract: A discarded/scrap WCP/Fe–C composites roller rings was re-melted in a 50kg medium frequency induction furnace, and a recycled composites was manufactured by centrifugal casting method using the composites re-melts. Dry sliding wear properties of the recycled composites have been investigated using a pin-on-disc wear tester at room temperature under loads of 50, 100 and 150N and sliding speeds of 60 and 80m/s. Results show that the microstructure of the recycled composites consists of un-dissolved WCP and bainite matrix. Wear rate of the recycled composites increases with the increase of load and sliding speed. And the friction coefficient of the recycled composites decreases with the increase of load and sliding speeds. The wear rate of the recycled composites almost is same as the primary composites, and the friction coefficient is obviously higher than that of the primary composites under same test conditions. Finally, the mechanisms of the dry sliding wear for the recycled composites are discussed. [Copyright &y& Elsevier]

Covalent organic frameworks (COFs) are an emerging class of functional nanostructures with intriguing properties, due to their unprecedented combination of high crystallinity, tunable pore size, large surface area, and unique molecular architecture. The range of properties characterized in COFs has rapidly expanded to include those of interest for numerous applications ranging from energy to environment. Here, a background overview is provided, consisting of a brief introduction of porous materials and the design feature of COFs. Then, recent advancements of COFs as a designer platform for a plethora of applications are emphasized together with discussions about the strategies and principles involved. Finally, challenges remaining for this type material for real applications are outlined. Covalent organic frameworks (COFs) are porous crystalline polymers with tunable composition and structural architecture, enabling precise control over functionality, density, and spatial arrangement. This universal control makes them a particularly promising platform for task‐led design. Recent advancements of COFs for numerous applications are reviewed and the challenges and opportunities associated with processing and large‐scale synthesis are discussed. [ABSTRACT FROM AUTHOR]

Step pyrolysis of N-rich industrial biowastes was used to explore decisive reaction pathways and regulatory mechanisms of NO x precursor formation. Three typical ones involving medium-density fiberboard waste (MFW), penicillin mycelia waste (PMW) and sewage sludge (SS) were employed to compare the formation characteristics of NO x precursors during one-step and two-step pyrolysis. Results demonstrated that considerable NH 3 -N predominated NO x precursors for one-step pyrolysis at low temperatures, depending on primary pyrolysis of labile amide-N/inorganic-N in fuels. Meanwhile, NO x precursors differed in the increment of each species yield while resembled in the total yield of 20–45 wt.% among three samples at high temperatures, due to specific prevailing reaction pathways linking with distinctive amide-N types. Subsequently, compared with one-step pyrolysis uniformly (800 °C), by manipulating intensities of reaction pathways at different stages (selecting differential intermediate feedstocks), two-step pyrolysis was capable of minimizing NO x precursor-N yield by 36–43% with a greater impact on HCN-N (75–85%) than NH 3 -N (9–37%), demonstrating its great capacity on regulating the formation of NO x precursors for industrial biowaste pyrolysis. These observations were beneficial to develop effective insights into N-pollution emission control during their thermal reutilization. [ABSTRACT FROM AUTHOR]

Hydrothermal treatment (HT) has been proved as a significant pretreatment in decreasing emissions of NO X pollutants from thermochemical utilization of sewage sludge (SS) derived solid fuel. This study aims to investigate the denitrification of HT and the redistribution of nitrogen (N) in different products so as to speculate the comprehensive pathway of N transformation during hydrothermal process. Results found that only 20% of N remained in hydrochar, whereas the rest of N (nearly 80%) was transformed into other phase. A majority of amino-N in SS was enriched in liquid phase in the form of Org-N at first, then further decomposed to NH 4 + -N. The remaining amino-N converted to pyrrole-N, pyridine-N and quaternary-N as temperature progresses. Meanwhile, amine-N derived from protein-N formed heterocyclic-N in oil phase via Diels-Alder reaction. NH 3 , the major nitrogenous gas, was dissolved in liquid as NH 4 + -N immediately after producing, but increased with prolonged reaction time. [ABSTRACT FROM AUTHOR]

The covalent organic frameworks (COFs) possessing high crystallinity and capability to capture low-concentration CO 2 (400 ppm) from air are still underdeveloped. The challenge lies in simultaneously incorporating high-density active sites for CO 2 insertion and maintaining the ordered structure. Herein, a structure engineering approach is developed to afford an ionic pair-functionalized crystalline and stable fluorinated COF (F-COF) skeleton. The ordered structure of the F-COF is well maintained after the integration of abundant basic fluorinated alcoholate anions, as revealed by synchrotron X-ray scattering experiments. The breakthrough test demonstrates its attractive performance in capturing (400 ppm) CO 2 from gas mixtures via O─C bond formation, as indicated by the in situ spectroscopy and operando nuclear magnetic resonance spectroscopy using 13 C-labeled CO 2 sources. Both theoretical and experimental thermodynamic studies reveal the reaction enthalpy of ≈-40 kJ mol -1 between CO 2 and the COF scaffolds. This implies weaker interaction strength compared with state-of-the-art amine-derived sorbents, thus allowing complete CO 2 release with less energy input. The structure evolution study from synchrotron X-ray scattering and small-angle neutron scattering confirms the well-maintained crystalline patterns after CO 2 insertion. The as-developed proof-of-concept approach provides guidance on anchoring binding sites for direct air capture (DAC) of CO 2 in crystalline scaffolds., (© 2024 Wiley‐VCH GmbH.)

Water pollution is a growing threat to humanity due to the pervasiveness of contaminants in water bodies. Significant efforts have been made to separate these hazardous components to purify polluted water through various methods. However, conventional remediation methods suffer from limitations such as low uptake capacity or selectivity, and current water quality standards cannot be met. Recently, advanced porous materials (APMs) have shown promise in improved segregation of contaminants compared to traditional porous materials in uptake capacity and selectivity. These materials feature merits of high surface area and versatile functionality, rendering them ideal platforms for the design of novel adsorbents. This Review summarizes the development and employment of APMs in a variety of water treatments accompanied by assessments of task-specific adsorption performance. Finally, we discuss our perspectives on future opportunities for APMs in water purification., (© 2022 Wiley-VCH GmbH.)

Albeit harnessing secondary sphere interactions to exert control over the reaction outcomes has primarily been applied to enzymatic and organometallic catalysis, there are seldom any studies that introduce outer-sphere modifiers into organocatalysts. This is even less in the corresponding heterogeneous catalytic system. In this contribution, we experimentally and computationally investigate the role of secondary effects in the reactivity of bromide anions toward CO 2 transformations. Six pyridinium cationic porous frameworks have been synthesized and fully characterized. Structure-activity relationships and kinetics show that the type and the location of the substituents on the cationic framework have a significant impact on the nucleophilic reactivity of their bromide counter anion. Specifically, the attachment of amine substituent to the ortho position relative to a pyridinium motif produces a remarkably efficient catalyst for CO 2 transformation, by a factor of six times greater in comparison to the pristine pyridinium-based polymer. The hydrogen-bond-interaction-promoted reagent activation and enhanced delocalization ability of bromide counter anion are believed to be the key to driving the reaction toward CO 2 utilization. These observations, therefore, champion the leverage of secondary interaction for optimizing the reactivity of organocatalysts.