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• Two fully nitrated triazoles were synthesized and studied. • The effect of backbones on energetic performance was revealed. • BITE-203 has a density of 1.968 g cm−3 and thermal stability of 168 °C. Despite their attractive energetic performances, fully nitrated monocyclic and fused compounds exhibit varying densities and stabilities. In this context, to reveal the effect of monocyclic and fused backbones on density and stability, two fully nitrated compounds, 1-trinitromethyl-3,5-dinitro-1,2,4-triazole (4) and 3,6-dinitro-7-(trinitromethyl)-[1,2,4]triazolo[4,3-b][1,2,4]trizole (8, BITE-203), with the same groups but different backbones were designed and synthesized via a simple three-step procedure. Experimental results, X-ray diffraction analysis, and quantum calculations indicated that fused BITE-203 exhibits a higher density (1.968 g cm−3 at 296 K) than monocyclic 4 (1.958 g cm−3 at 296 K), which is caused by the stronger intermolecular p-π interactions and closer molecular stacking of BITE-203. In addition, BITE-203 also shows higher stability (168 °C) than 4 (143 °C) owing to its weaker intramolecular repulsion and stronger aromaticity, thus revealing the positive effect of the fused backbone on density and stability enhancement. In addition, BITE-203 is the only trinitromethyl compound that simultaneously achieves a density greater than 1.950 g cm−3 and a thermal decomposition temperature exceeding 165 °C, in addition to a considerable detonation velocity of 9199 m s−1 and high oxygen balance of + 27.6%, demonstrating its excellent potential as a promising high-energy–density material. [ABSTRACT FROM AUTHOR]

• Positional isomerism is a promising strategy to enhance the densities of energetic materials. • The density of the isomer is more than 0.08 g cm-3 higher than that of original material. • Crystal structures and intermolecular interactions were studied to investigate the mechanism. Development of high-density energetic materials has drawn considerable attention because the densities significantly affect their detonation performance. Herein, we propose an effective strategy based on positional isomerism for enhancing the densities of pre-existing energetic materials by optimizing their structures to reinforce intermolecular interactions. By applying this strategy, we design and synthesize 2-amino-5-nitramino-1,3,4-oxadiazole (2), a suitable isomer of 3-amino-5-nitramino-1,2,4-oxadiazole (1). This isomer is the first example of a monocyclic nitramino 1,3,4-oxadiazole reported to date. Single-crystal X-ray diffraction reveals that the isomer has a high crystal density (1.938 g cm−3 at 110 K), which is 0.083 g cm−3 greater than that of the original material (1 , 1.855 g cm−3 at 110 K). Mechanistic studies confirmed that the isomer possesses stronger intermolecular hydrogen-bonding and π − π interactions, resulting in denser stacking, smaller cell volume, and thus, higher density. Remarkably, the isomer has a very short intermolecular hydrogen bond (1.956 Å), which is significantly shorter than that of 1 (2.133 Å) and other representative strongly hydrogen-bonded energetic materials such as 2,4,6-triamino-1,3,5-trinitrobenzene (TATB, 2.239 Å) and 1,1-diamino-2,2-dinitroethylene (FOX-7, 2.143 Å). Moreover, this strategy can be applied to its energetic salts. The higher densities of the isomer and its salts endow better detonation performance. Particularly, the detonation velocity of the isomer is more than 400 m s−1 higher than that of the original material (8668 m s−1 for 2 vs 8250 m s−1 for 1). Meanwhile, the hydroxylammonium salt 2b exhibits a high detonation velocity of 9087 m s−1, which is superior to that of 1,3,5-trinitroperhydro-1,3,5-triazine (RDX). [ABSTRACT FROM AUTHOR]

Abstract: Chemical-looping combustion (CLC) has been recognized as an energy-efficient method for CO2 capture. For calcium sulfate (CaSO4) oxygen carrier, the rapid fall in the mechanical strength and reactivity limits its application in CLC. In this study, Taguchi robust design method with L 9 orthogonal array was implemented to optimize extrusion condition for the preparation of binder-supported CaSO4 oxygen carriers. The orthogonal experiment results showed the addition of SB powder enhanced both mechanical strength and conversion of CaSO4, and the optimal extrusion condition was 30g CaSO4, 12g SB powder, 2.5mL acetic acid, and 15mL water. The favorable oxygen carriers were comprehensively studied in a fixed bed reactor. The results of reduction test showed the mass-based reaction rates of the binder-supported CaSO4 were significantly increased, because the fresh samples had the higher surface area which was evidenced by pore structure analysis. Moreover, the favorable performance of binder-supported CaSO4 was explained by formation of CaAl2O4 which had excellent thermal stability and provided a stable nanosized framework between the crystal grains observed by field emission scanning electron microscope (FESEM). [Copyright &y& Elsevier]

The presence of Li 2 S 3 in ether-based electrolyte and two energy barriers in sulfur reduction at 25 and 50% depth of discharge are confirmed by electrochemical impedance spectroscopy. [Display omitted] • Flexible free-standing films with high sulfur loadings are assembled by phase inversion process. • Sulfur reduction pathways in a lithium-sulfur cell are studied by electrochemical impedance spectroscopy. • The presence of Li 2 S 3 in ether-based electrolyte is confirmed. • Two energy barriers are found at 25% and 50% depth of discharge. A comprehensive understanding of sulfur reduction pathways is critical to developing high-performance lithium-sulfur (Li-S) batteries. However, to date even the polysulfide intermediates are not fully understood with their distinct forms under debate. In this work, electrochemical impedance spectroscopy is employed to study the polysulfide evolution in a Li-S cell using the free-standing film with a sulfur loading of 6 mg cm−2 and ether-based electrolyte. The impedance data reveal the presence of soluble Li 2 S 3 intermediate, and two major obstacles in the discharge processes. One obstacle is the sluggish kinetics of Li 2 S 4 reduction reaction at 25% depth of discharge (DoD), and the other is Li 2 S nucleation observed at 50% DoD requiring to overcome an energy barrier. This clarification provides a new prospect for making a better Li-S battery, i.e. to develop effective sulfur reduction catalysts that circumvent the two major obstacles. [ABSTRACT FROM AUTHOR]

[Display omitted] • A highly thermostable zwitterionic energetic molecule 6 features layer-by-layer packing. • The ionic derivative 7 exhibits good detonation performances and low mechanical sensitivities. • Constructing fused N-rich heterocycles with zwitterionic hydrogen-bonded networks aids in searching heat-resistant CHN materials. Two energetic zwitterionic CHN compounds 5-(1,3-diamino-5-iminio-1,5-dihydro-4H-1,2,4-triazol-4-yl)tetrazole (5) and 5-(6,7-diamino-3-iminio-3H-[1,2,4]triazolo[4,3-b][1,2,4]triazol-2(7H)-yl)tetrazole (6) were synthesized effectively by using a straightforward one-step synthetic route. With a rational arrangement of amino and tetrazole units as hydrogen bond (HB) donors and acceptors, 6 has more HB acceptors and displays a layer-by-layer structure. In comparison, the crystal packing of 5 displays twisted layers. In addition, the N-amino group of 6 contributes to inter-layer hydrogen-bonded interactions, thereby giving rise to a three-dimensional hydrogen-bonded network. Benefiting from unique structural features, the decomposition temperature of 6 is 371 °C, which approaches the relatively excellent among energetic ternary CHN compounds. Additionally, 6 exhibits good detonation performance and low impact sensitivity. This unique molecular structure, incorporating a fused nitrogen-rich zwitterionic 3D hydrogen-bonded interaction, provides a promising pathway for the development of high-nitrogen energetic materials. [ABSTRACT FROM AUTHOR]

• An effective strategy based on isomerism for determining the direct effects of HB interactions was presented. • Stronger intermolecular HB interactions are conducive to an increase in density, whereas stronger intramolecular HB interactions are conducive to a thermostability increase. • Isomers 3a and 3b could be applied as insensitive heat-resistant energetic materials. Introduction of additional donors or acceptors for strengthening hydrogen-bonding (HB) interactions is one of the most commonly utilized methods to improve the density and thermostability of organic functional materials, including energetic materials. However, this method can lead to changes in the molecular composition, obscuring the direct effects of HB. To address this issue, we propose an effective strategy, based on isomerism, for determining the direct effects of HB interactions. We designed and synthesized two isomers, 2,4,6,8-tetranitro-1,5-diamine-naphthalene (3a) and 1,3,6,8-tetranitro-2,7-diamine-naphthalene (3b). X-ray diffraction analysis, quantum calculations, and experimental investigations revealed that 3a , which has stronger a intermolecular HB, exhibits closer molecular packing and, thus, a higher density (1.905 g cm−3) than 3b (1.840 g cm−3). By contrast, 3b , which has a stronger intramolecular HB, exhibits a higher degree of aromaticity and, thus, a higher thermostability (decomposition temperature (T d) = 330 °C) than 3a (T d = 256 °C). Thus, after eliminating interference from compositional changes, it is clear that stronger intermolecular HB interactions are conducive to an increase in density, whereas stronger intramolecular HB interactions are conducive to a thermostability increase. In addition, the densities and thermostabilities of 3a and 3b are high, and the preparation method is simple, involving only two steps. Both compounds are highly insensitive (IS > 40 J and FS > 360 N), and the detonation performance is comparable to that of HNS and PYX. These results strongly suggest that 3a and 3b could be applied as insensitive heat-resistant energetic materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • The constructed system was sensitive to the tumor microenvironment. • PTT and CDT was reinforce each other to achieve synergistic treatment of tumors. Chemodynamic therapy (CDT) and photothermal therapy (PTT) are important adjunctive therapeutic approaches for tumors, complementing conventional methods like chemotherapy and radiotherapy. They play a crucial role in inhibiting tumor proliferation and metastasis. In this study, we established a combinational therapy strategy involving PTT and CDT for in situ and metastatic melanoma in experimental murine models. As-prepared S@M−EF system incorporated EGCG, a bioactive natural compound, known for its anti-tumor properties, which coordinated with FeIII to form an acidity-sensitive metal–organic framework (MPN). Sorafenib (SRF) was loaded in the system and released in the tumor microenvironment to work synergistically with FeIII and enhance the ferroptosis effect. Mesoporous polydopamine (MPDA) components inside S@M−EF exhibited photothermal characteristics. We conducted systematic in vitro and in vivo studies to assess the specificity and therapeutic effect of various S@M conjugates. Cellular examination confirmed that tumor cell ferroptosis could be induced and temperature could be increased due to photothermal conversion, and these two effects reinforced with each other. S@M−EF induced higher cell apoptosis compared to single functionalized conjugates (S@M, SRF, or M−EF). Enhanced therapeutic efficacy in melanoma and its metastasis was confirmed in murine models. This tumor microenvironment-responsive nanoplatform, based on natural molecules, combined CDT and PTT, offering a mutually enhanced treatment method for inhibiting tumor proliferation and metastasis. [ABSTRACT FROM AUTHOR]

This article demonstrates the fabrication of the eco-friendly g-C 3 N 4 /CNCs-H hydrogel reinforced with CNCs and g-C 3 N 4 as smart adsorption hydrogel with excellent mechanical, thermal, swelling response and outstanding adsorption capacity. The adsorption mechanism is proposed to involve synergism between π-π stacking and hydrogen-bonding interactions. • A novel g-C 3 N 4 /CNCs-H hydrogel was designed. • CNCs were fabricated by deep eutectic solvent and high-pressure homogenization. • Properties of the hydrogels were investigated systematically. • Adsorption isotherms and kinetics were studied. • Plausible adsorption mechanism and synergetic effects were further discussed. The eco-friendly sodium carboxymethylcellulose (CMC-Na)/polyvinyl alcohol (PVA) hydrogel reinforced with cellulose nanocrystal (CNC) and graphitic-like carbon nitride (g-C 3 N 4) was firstly prepared as smart adsorption hydrogel with mechanical, thermal and swelling response. Encouragingly, the mechanical properties of the g-C 3 N 4 /CNCs-H hydrogel were enhanced with simply changing the content of g-C 3 N 4. The 1.0% g-C 3 N 4 /CNCs-H hydrogel had outstanding tensile strength (up to 648 KPa), excellent elongation (1169%) and satisfactory toughness (340 KJ/m3). These enhancements were due to the inherently superior properties of the prepared CMC-Na/PVA and the synergistic effect of strong hydrogen bonding interactions between g-C 3 N 4 , CNCs and CMC-Na/PVA chains. The as-prepared g-C 3 N 4 /CNCs-H hydrogel has high equilibrium swelling capacity (90.47–117.3 g/g), which greatly improved the adsorption capacity of methylene blue (MB, q e > 198.6 mg/g). The adsorption properties of MB on the as-prepared hydrogel fitted well with the pseudo-second-order kinetic model and the Langmuir isotherm model. It was showed that the interaction of π-π stacking and hydrogen bonds resulted in the high adsorption capacity of the hydrogels. This study presented a basis and demonstration for the application of hydrogels in contaminants removal in poisonous waterbodies. [ABSTRACT FROM AUTHOR]

[Display omitted] • Bi 2 O 3 @Cu-MOF was used for photocatalytic inactivation of K. mikimotoi. • When n (Cu2+): n (Bi3+) was 2: 1, the photocatalytic activity was better. • Photocatalytic inactivation efficiency of K. mikimotoi was 96.35%. • Inactivation mechanism of K. mikimotoi was proposed. Numerous studies have shown that Karenia mikimotoi (K. mikimotoi) is the main toxic red tide algae in the ocean and photocatalytic technology has gradually been considered to be an effective way to inactivate harmful algae. In this study, a Bi 2 O 3 @copper metal organic framework (Cu-MOF) was successfully prepared by loading Bi 2 O 3 on a Cu-MOF for inactivation of K. mikimotoi under visible light. The band gap of Bi 2 O 3 @Cu-MOF decreased from 2.57 eV to 2.33 eV with the loading of Cu-MOF, which increased the absorption of visible light. The specific surface area of Bi 2 O 3 @Cu-MOF was 276.604 m2/g, and the mesoporous pore size was reduced to 4 nm. When n (Cu2+): n (Bi3+) was 2: 1, Bi 2 O 3 @Cu-MOF-1 (60 mg/L) showed better photocatalytic activity under visible light irradiation for 4 h, and 96.35 % of K. mikimotoi was inactivated. The content of the two chlorophylls decreased by approximately 2 mg/L after 4 h of photocatalysis, the soluble protein decreased from 0.166 mg/L to 0.039 mg/L, and the antioxidant system was also damaged. The main free radicals were shown to be O 2 − and OH while the survival rate of algae cells increased by 8.273 % and 6.273 %, respectively. MOF-coupled photocatalysts have great potential for the photocatalytic treatment of harmful algae. [ABSTRACT FROM AUTHOR]

CaO-based sorbents are considered suitable candidates for cyclic CO 2 capture at high temperatures. However, the CO 2 capture capacities of natural CaO-based sorbents decrease sharply after only a few cycles. This paper presents a novel wet mixing combustion synthesis to improve the cyclic CO 2 capture performance of CaO-based sorbents. Results show that preparation conditions significantly affected the cyclic performance of the sorbents. The optimal molar ratios of calcium to magnesium and fuel to metal oxides were 2 and 0.5, respectively, for the preparation process. The wet mixing combustion synthesis did not show the highest CO 2 capture capacity in comparison to the sol–gel combustion synthesis, however, the proposed method is still valid due to the low cost of the materials used. The sorbent prepared by the new method could achieve relatively stable cyclic CO 2 capture behavior, and showed a porous microstructure that can be maintained during cyclic reactions. The capture capacity of the sorbent obtained a 0.4 g CO 2 /g sorbent after 50 cycles. [ABSTRACT FROM AUTHOR]

• TCS affected SCFA production from sludge anaerobic fermentation system. • Appropriate level TCS increased SCFA production by enhancing acidogenesis. • High level TCS inhibited SCFA production. • TCS didn't change the structure of anaerobic fermentation microbial community. • Suitable TCS up-regulated the expression of acidogenesis-related enzymes. Triclosan (TCS) is an emerging contaminant in waste activated sludge (WAS). However, the effects of TCS on WAS anaerobic fermentation is still unknown. Herein, we investigated the impacts of different TCS levels on the short-chain fatty acid (SCFA) accumulation. TCS at 100 mg/kg TSS (total suspended solids) significantly (p < 0.05) enhanced SCFA production by 35.8 ± 4.1% through increasing the production of propionic and butyric acid, while the higher TCS level inhibited the SCFA production processes. The results of batch tests with real sludge showed that 100 mg/kg TSS TCS enhanced acidogenesis process and had no significant impact on other processes, while higher TCS level caused negative effects on acidogenesis, acetogenesis and methanogenesis. Generally, 2,4-dichlorophenol was considered as the main metabolic product of TCS under anaerobic condition. However, in this study, TCS was found to be converted into (Z)-4-(2,4-dichlorophenoxy)penta-1,3-dien-3-ol, 2,4-dichloro-1-(4-chloro-2-methoxyphenoxy)benzene and other substances, and its hypothetical metabolic pathway were reformulated. The microbial community structure in the WAS anaerobic fermentation system did not significantly change with TCS addition, but 100 mg/kg TSS TCS contributed to the modest enrichment of SCFA producers. Further analyses of key enzyme activity and abundance of enzyme-encoded genes revealed that TCS at 100 mg/kg TSS up-regulated the expression of enzyme-coding genes (i.e. butyrate kinase (BK) and oxaloacetic acid carboxylase (OAATC)), and this is the primary reason for the increased SCFA production. This work provides a new insight for pollutant effects in WAS anaerobic fermentation, which will help to reveal the impact of emerging contaminants and relearn the role of conventional pollutants. [ABSTRACT FROM AUTHOR]