Electrical stress and acid orange 7 synergistically clear the blockage of electron flow in the methanogenesis of low-strength wastewater.

Energy recovery from low-strength wastewater through anaerobic methanogenesis is constrained by limited substrate availability. The development of efficient methanogenic communities is critical but challenging. Here we develop a strategy to acclimate methanogenic communities using conductive carrier (CC), electrical stress (ES), and Acid Orange 7 (AO7) in a modified biofilter. The synergistic integration of CC, ES, and AO7 precipitated a remarkable 72-fold surge in methane production rate compared to the baseline. This increase was attributed to an altered methanogenic community function, independent of the continuous presence of AO7 and ES. AO7 acted as an external electron acceptor, accelerating acetogenesis from fermentation intermediates, restructuring the bacterial community, and enriching electroactive bacteria (EAB). Meanwhile, CC and ES orchestrated the assembly of the archaeal community and promoted electrotrophic methanogens, enhancing acetotrophic methanogenesis electron flow via a mechanism distinct from direct electrochemical interactions. The collective application of CC, ES, and AO7 effectively mitigated electron flow impediments in low-strength wastewater methanogenesis, achieving an additional 34% electron recovery from the substrate. This study proposes a new method of amending anaerobic digestion systems with conductive materials to advance wastewater treatment, sustainability, and energy self-sufficiency.

Molten salt-confined pyrolysis towards heteroatom-doped porous carbon nanosheets for high-energy-density Zn-ion hybrid supercapacitors.

Carbon nanosheets with heteroatom doping and well-developed porosity exhibit broad application foreground for Zn-ion hybrid supercapacitors (ZHSCs), but the simple and controllable preparation is still of great challenge. In this study, by using LiCl-KCl as in-built templates, histidine as carbon and nitrogen sources, and KNO3, K2SO4, KOH or Na2S2O3 as active agent, a series of N and NS doped porous carbon nanosheets are developed. Results indicate that, with the activator introduction, pore structures of the carbonized products are notably boosted, showing an astounding 30-244 % increase in BET specific surface area, and meanwhile, heteroatom with a content of ca. 12 % can be doped into the resultant carbon skeletons. Specifically, the NSPCN-800 (activated by Na2S2O3) with a large specific surface area of 1297 m2/g, a hierarchically porous structure composed of abundant micropores and mesopores, and a suitable heteroatom content (N: 11.9 wt%; S: 0.6 wt%) presents an impressive energy storage behavior as cathode for ZHSCs, including a specific capacitance of 165.8F/g, a specific capacity of 95.2 mAh/g, an energy density of 59.0 Wh kg-1 and a cyclic stability with a 82.6 % capacity retention after 5000 cycles. These performance parameters surpass numerous reported ZHSCs, making NSPCN-800 a very promising cathode for practical use.

Metal-organic frameworks-derived carbon modified wood carbon monoliths as three-dimensional self-supported electrodes with boosted electrochemical energy storage performance.

Wood-derived carbon monoliths, in recent years, have attracted tremendous interest in the field of energy storage, but their electrochemical characteristics are still far from satisfactory. Here, we report a universal and efficient approach for the preparation of structure-engineered, heteroatom-functionalized and property-boosted wood carbons. A two-step ion-exchange process greatly enriches the nucleation sites of ZIF-8 on the inner wall of wood tracheids, hence leading to a unique carbon/carbon heterostructure after carbonizing and acid-washing. Particularly, the prepared NPCM-900 with a large specific surface area of 708.2 m2 g-1, a hierarchical porous architecture and a suitable N content of 2.3% delivers an ultrahigh area-normalized specific capacitance of 23.7 F cm-2 at 5 mA cm-2, which stands for a new capacitive record among the wood-based binder-free electrodes. The NPCM-900//NPCM-900 all-solid-state supercapacitor has an admirable energy density of 9.3 Wh m-2 at 24.9 W m-2 and a large power density of 248.3 W m-2 at 4.8 Wh m-2, while the NPCM-900 based Zn-ion hybrid supercapacitor (NPCM-900//Zn) exhibits a superior energy density of 12.7 Wh m-2. Furthermore, the NPCM-900//NPCM-900 and NPCM-900//Zn present great stabilities with capacitance retentions of 87% and 85%, respectively, after 5000 cycles. These parameters notably outperform those of most wood-based supercapacitors, endowing the NPCM-900 with extensive prospects for practical use.

In Situ Formation of Micropore-Rich Titanium Dioxide from Metal-Organic Framework Templates.

Phase and porosity control in titanium dioxide (TiO2) is essential for the optimization of its photocatalytic activity. However, concurrent control over these two parameters remains challenging. Here, a novel metal-organic framework templating strategy is demonstrated for the preparation of highly microporous anatase TiO2. In situ encapsulation of Ti precursor in ZIF-8 cavities, followed by hydrolysis and etching, produces anatase TiO2 with a high Brunauer-Emmett-Teller surface area of 335 m2·g-1 and a micropore surface area ratio of 48%. Photocatalytic hydrogen generation catalyzed by the porous TiO2 can reach a rate of 2459 µmol·g-1·h-1. The measured photocatalytic activity is found to be positively correlated to the surface area, highlighting the importance of porosity control in heterogeneous photocatalysts.

Confinement of Aggregation-Induced Emission Molecular Rotors in Ultrathin Two-Dimensional Porous Organic Nanosheets for Enhanced Molecular Recognition.

Despite the rapid development of molecular rotors over the past decade, it still remains a huge challenge to understand their confined behavior in ultrathin two-dimensional (2D) nanomaterials for molecular recognition. Here, we report an all-carbon, 2D π-conjugated aromatic polymer, named NUS-25, containing flexible tetraphenylethylene (TPE) units as aggregation-induced emission (AIE) molecular rotors. NUS-25 bulk powder can be easily exfoliated into micrometer-sized lamellar freestanding nanosheets with a thickness of 2-5 nm. The dynamic behavior of the TPE rotors is partially restricted through noncovalent interactions in the ultrathin 2D nanosheets, which is proved by comparative experimental studies including AIE characteristics, size-selective molecular recognition, and theoretical calculations of rotary energy barrier. Because of the partially restricted TPE rotors, NUS-25 nanosheets are highly fluorescent. This property allows NUS-25 nanosheets to be used as a chemical sensor for the specific detection of acenaphthylene among a series of polycyclic aromatic hydrocarbons (PAHs) via fluorescent quenching mechanism. Further investigations show that NUS-25 nanosheets have much higher sensitivity and selectivity than their stacked bulk powder and other similar polymers containing dynamic TPE rotors. The highly efficient molecular recognition can be attributed to the photoinduced electron transfer (PET) from NUS-25 nanosheets to acenaphthylene, which is investigated by time-resolved photoluminescence measurements (TRPL), excitation and emission spectra, and density functional theory (DFT) calculations. Our findings demonstrate that confinement of AIE molecular rotors in 2D nanomaterials can enhance the molecular recognition. We anticipate that the material design strategy demonstrated in this study will inspire the development of other ultrathin 2D nanomaterials equipped with smart molecular machines for various applications.

Improving Water-Treatment Performance of Zirconium Metal-Organic Framework Membranes by Postsynthetic Defect Healing.

Microporous metal-organic frameworks (MOFs) as building materials for molecular sieving membranes offer unique opportunities to tuning the pore size and chemical property. The recently reported polycrystalline Zr-MOF membranes have greatly expanded their applications from gas separation to water treatment. However, Zr-MOFs are notoriously known for their intrinsic defects caused by ligand/cluster missing, which may greatly affect the molecular sieving property of Zr-MOF membranes. Herein, we present the mitigation of ligand-missing defects in polycrystalline UiO-66(Zr)-(OH)2 membranes by postsynthetic defect healing (PSDH), which can help in increasing the membranes' Na+ rejection rate by 74.9%. Intriguingly, the membranes also exhibit excellent hydrothermal stability in aqueous solutions (>600 h). Our study proves the feasibility of PSDH in improving the performance of polycrystalline Zr-MOF membranes for water-treatment applications.

Hydroxyl ammonium ionic liquids synthesized by water-bath microwave: synthesis and desulfurization.

Water-bath microwave method was used for hydroxyl ammonium ionic liquids (ILs) synthesis to study the removal of sulfur dioxide (SO(2)) from the flue gas. The results showed that the water-bath microwave method has some advantages of short reaction time and good yields. The synthesis of ethanolamine lactate ILs was fundamentally studied by an orthogonal experiment design (L(9)(3(4))). Based on statistic analysis, it is revealed that the molar ratio of ammonium/acid is the most significant variable, and the optimized preparation conditions are under 338 K, wave power of 300 W for 30 min with the molar ratio 1:1.1 (ethanolamine vs. lactic acid). At the same condition, the yield of the other ILs was over 90% except dimethyl ethanolamine-based ILs. Results showed that the solubility of SO(2) in ethanolamine lactate ILs was 0.51 (mole fraction), higher than others. Ethanolamine lactate ILs was a better absorbent for SO(2). The optimal temperature for the absorption and desorption process were 298 and 363 K, respectively. The optimal desorption time was 60 min. It was also found that water-bath microwave can improve the release of the absorbed SO(2) from ILs.