Development of closed‐loop chemically recyclable plastics (CCRPs) that can be widely used in daily life can be a fundamental solution to the global plastic waste crisis. Hence, it is of great ...significance to develop easy‐to‐recycle CCRPs that possess superior or comparable material properties to the commodity plastics. Here, a novel dual crosslinked CCRP, namely, supramolecular covalent adaptable networks (supra‐CANs), is reported, which not only displays mechanical properties higher than the strong and tough commodity polycarbonate, but also exhibits excellent solvent resistance as thermosets. The supra‐CANs are constructed by introducing reversible noncovalent crosslinks into the dynamic covalent polymer networks, resulting in highly stiff and strong thermosets that also exhibit thermoplastic‐like ductile and tough behaviors as well as reprocessability and rehealability. In great contrast, the analogs that do not have noncovalent crosslinks (CANs) show elastomeric properties with significantly decreased mechanical strength. Importantly, the developed supra‐CANs and CANs can be converted back into the initial monomers in high yields and purity at room temperature, even with additives, which enables the sustainable polymer‐monomer‐polymer circulation. This work provides new design principles for high‐performance chemically recyclable polymers as sustainable substitutes for the conventional plastics.
Supramolecular covalent adaptable networks (supra‐CANs) with room‐temperature closed‐loop recyclability are constructed by introducing reversible noncovalent crosslinks into the dynamic covalent polymer networks, resulting in strong and stiff thermosets that also exhibit thermoplastic‐like ductility and toughness, as well as reprocessability and rehealability. The mechanical properties of the supra‐CANs are superior to those of strong and tough commodity polycarbonate.
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•A new kind of carbon nanofibers bearing Fe/Co alloy nanoparticles is fabricated.•Fe/Co-CNFs electrode achieves a total degradation of tetracycline into CO2 and H2O.•Fe/Co-CNFs ...display outstanding stability, recyclability and reusability.
Rough surfaced carbon nanofibers bearing evenly distributed iron/cobalt alloy nanoparticles (Fe/Co-CNFs) are developed through the electrospinning of polyvinylpyrrolidone (PVP) mingled with 5.0 wt% of total ferric nitrate and cobalt nitrate concentration, followed by direct calcination of PVP composite nanofibers at 800 °C for 30 min in a reduction atmosphere. With a large specific surface area and active sites, the Fe/Co-CNFs could serve as an excellent anode material for the complete electrocatalytic degradation of tetracycline into carbon dioxide and water at a bias voltage of 1.0 V (vs. SCE) in a solution with pH value of 5.0 and 0.1 mol L−1 Na2SO4 as the supporting electrolyte. The observed tetracycline degradation percentage of 97.55% even after ten cycles of electrocatalytic process for Fe/Co-CNFs modified electrode indicates an excellent stability, recyclability, and reusability. This work provides a novel material for environmental remediation of antibiotic contaminated water.
The Front Cover depicts in an artistic manner the structure of a heterogeneous catalyst specifically tailored for Ullmann C−O type cross‐couplings. In this material, the functionalization of graphite ...nanoplatelets with a polyaminic linker allowed the stabilization of Cu single atoms. The designed catalyst showed excellent activity, selectivity, recyclability, and flexibility toward various substrates in Ullmann‐based C−O type transformations. More information can be found in the Research Article by G. Vilé and co‐workers.
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•Vitrimers are made from two renewable resources, lignin and epoxidized linseed oil.•Bio-based vitrimer composites are described as new green adhesives.•Vitrimers have shear lap ...strengths of about 10–17 MPa.•Bio-based adhesives are reprocessable, reweldable and biodegradable.
The market of epoxy resin-based adhesives is constantly growing in the automotive, electronics, and healthcare industries thanks to their unique features such as high bonding strength, durability, and corrosion resistance. In this work, alternative sustainable vitrimer adhesives, containing from 20 to 50 wt% of lignin microparticles, were prepared from epoxidized linseed oil (ELO) and a boronic ester dithiol crosslinker (DBEDT), in the absence of solvents and catalysts. The addition of unmodified commercial Kraft lignin to the composites directly influences their thermal and mechanical properties and determines their bonding capacity between several adherent substrates, also affecting the rewelding potential. The lignin-vitrimer composites and the corresponding neat vitrimer matrix exhibited values of lap shear strengths in the range of 9 to 17 MPa, when tested as adhesives with aluminum, stainless steel, and wood specimens, and good to excellent rewelding capability. The amount of lignin microparticles influences the balance between cohesive and adhesive forces during the separation of the adhered aluminum surfaces and the eventual joint failure. In the case of the composites with 20 wt% of lignin, lap shear strength remains constant even after four cycles of rebonding via compression molding, indicating that the best rewelding performance is associated with previous cohesive failure when the adhesive remains on both aluminum sheets' surfaces. In addition, the adhesion was preserved for 83 % of the initial value after 24 h immersed in water. Importantly, biodegradability in both soil and seawater was enhanced by the presence of the lignin filler. In summary, the simple preparation strategy of bio-based vitrimer composites coming from two natural sources could pave the way to green alternatives for industrial applications, such as epoxy-based adhesives.
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•In organometallic catalytic chemistry, most catalysts are dissolved in organic solvents to ensure their activity.•The catalysts, however, cannot be recycled from the reaction system ...after several turnovers, which is a waste of the noble metals.•Metal–organic frameworks (MOFs), with the periodic order and site isolation of the catalytic struts, eliminate the multimolecular catalyst deactivation, thus extending the catalytic centers’ functional lifetime.•Meanwhile, MOFs can facilitate reactions like enzymatic catalysis due to their organization of the reactants in suitable positions and their ability to minimize the entropy loss and to reduce the transition-state energy.•In this review, typical examples of MOF-catalyzed reactions are given to show the increasingly visible advantage of MOFs in catalytic reactions.•Classification of the catalytic centers, how they work for various reactions in porous MOFs, as well as how to control their selectivity and activity will be discussed in detail.•Furthermore, functional groups introduced to MOFs by different post-synthetic catalytic reactions are discussed thoroughly.
Metal-organic frameworks (MOFs), as a new stable class of hybrid materials synthesized, regulated and decorated by rational incorporating organic bridging ligands and metal ions with well-defined coordination geometry have become promising candidates for heterogeneous catalysis in industrial applications. Compared with homogeneous catalysts, MOF catalysts can be easily recycled and reused for several times; while compared with traditional heterogeneous catalysts, they possess tunable size and catalytic centers via exchange or modification of their components. This review will sketch typical successful MOF-catalyzed reactions and summarize various catalytic centers, including the open metal sites, bifunctional acid-base sites in MOFs, as well as catalytic centers introduced to MOFs via PSM. The periodic order and site isolation of the catalytic struts in MOFs eliminate the multimolecular catalyst deactivation pathways to extend the catalytic centers’ functional lifetime and facilitate the studies of their activities and reaction mechanisms. Furthermore, detailed discussion on how the catalytic centers play the roles in the catalytic reactions and how to control the activity and selectivity of them will be given via typical reported examples.
To date, various stretchable conductors have been fabricated, but simultaneous realization of the transparency, high stretchability, electrical conductivity, self‐healing capability, and sensing ...property through a simple, fast, cost‐efficient approach is still challenging. Here, α‐lipoic acid (LA), a naturally small biological molecule found in humans and animals, is used to fabricate transparent (>85%), electrical conductivity, highly stretchable (strain up to 1100%), and rehealable (mechanical healing efficiency of 86%, electrical healing efficiency of 96%) ionic conductor by solvent‐free one‐step polymerization. Furthermore, the ionic conductors with appealing sensitivity can be served as strain sensors to detect and distinguish various human activities. Notably, this ionic conductor can be fully recycled and reprocessed into new ionic conductors or adhesives by a direct heating process, which offers a promising prospect in great reduction of electronic wastes that have brought acute environmental pollution. In consideration of the extremely facile preparation process, biological available materials, satisfactory functionalities, and full recyclability, the emergence of LA‐based ionic conductors is believed to open up a new avenue for developing sustainable and wearable electronic devices in the future.
α‐Lipoic acid (LA), a naturally small biological molecule found in humans and animals, is first used to fabricate ionic conductors with high transparency, ultrahigh stretchability, conductivity, fast self‐healing capability, and high strain sensitivity through a facile, solvent‐free one‐step polymerization. Notably, these ionic conductors can be fully recycled and reprocessed into new ionic conductors or adhesives by a direct heating process.
A new protocol for constructing sandwich-like SiO
-Ag@TiO
hollow spheres (SAT) is introduced, in which SiO
acts as an efficient support for the Ag nanoparticles (Ag NPs) immobilization, while TiO
...maintains its hierarchical structure and prevents the aggregation of Ag NPs during the photocatalytic reaction. As a photocatalytic agent, the inner and outer surfaces of TiO
can be fully occupied by pollutants molecules because of its unique structure, which faster boosts the photo-generated electrons to transfer the substrates, leading to an enhanced photocatalytic performance. Compared with Ag NPs deposited on the surface of SiO
@TiO
(STA), the as-synthesized SAT exhibits a markedly enhanced visible-light and UV light activity than STA for degrading tetracycline and traditional dyes. The excellent photocatalytic performances are ascribed to the enhanced transport paths of photo-generated electrons, reduced recombination probability of e
/h
pairs, and decreased threat of oxidation and corrosion. Especially, the SAT still maintains its photocatalytic efficiency after five consecutive runs even though the sample is recovered under visible-light irradiation, far beyond the reusability of STA under the same conditions. Therefore, the outstanding photocatalytic activity and excellent recyclability make SAT more potential to purify aquatic contaminants and to meet the demands of future environmental issues.
Covalent polymers connected by non-covalent interactions constitute a fascinating set of materials known as supramolecular polymer networks (SPNs). A key feature of SPNs is that the underlying ...covalent polymers endow the resulting self-assembled materials with features, such as structural and mechanical integrity, good processability, recyclability, stimuli-responsiveness, self-healing, and shape memory, that are not recapitulated in the case of classic covalent polymer systems. The unique nature of SPNs derives from the controlled marriage of traditional covalent polymers and macrocycle-based host–guest interactions. As a consequence, supramolecular polymeric networks have played important roles in a number of diverse fields, including polymer science, supramolecular chemistry, materials science, biomedical materials, and information storage technology. In this Review, we summarize advances made in the area of functional SPNs, with a focus on original literature reports appearing in the past five years. The treatment is organized according to the key macrocycle-based host–guest interactions used to produce various SPNs. The role of the underlying polymer backbones is also discussed.
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The current study provides a novel insight into the role of synergism of the changes in Mg2+/ Al3+ in the best catalytic activity of indol-3-yl derivatives. A series of Co-Mg-Al ...layered triple hydroxides (LTHs) catalysts were produced by altering the Al3+/Mg2+ ratio with respect to Co2+. The physicochemical properties of LTHs were well characterized by ICP-AES, XRD, FTIR, FE-SEM, BET, Zeta-sizer, and VSM. The results show that the sample CMA4 (Co2+:Mg2+:Al3+ 2:4:4) is an exception to the physicochemical characteristics of the produced Co-Mg-Al LTHs, which is due to the synergism between the changes in Mg2+ and Al3+. To the best of our knowledge, this is the first study to report the synthesis of indol-3-yl derivatives from indole-3-carbaldehyde using Co-Mg-Al LTHs as highly efficient heterogeneous catalysts, which is an extremely appealing path. The selectivity of the synthesis was studied by condensing various nucleophiles through the one-pot method that established superior reactivity under mild conditions. Notably, the results show that the Co-Mg-Al LTHs system exhibited an extraordinarily catalytic activity, with the highest yield (98%) being obtained under the following optimal conditions: the concentration of Co-Mg-Al LTHs = 5 mol%, 30 min., water/ethanol as solvent. Furthermore, the reusable studies exhibited that the catalysts were found to be stable and reusable for up to six cycles without substantial loss of catalytic activity. Finally, a plausible reaction mechanism of the Co-Mg-Al LTHs system for indol-3-yl derivatives was put forward according to our comprehensive analysis. Our work illuminates a cheap and flexible strategy for the synthesis of indol-3-yl derivatives using Co-Mg-Al LTHs.
