Dongguan University of Technology

Hydrogen-bonded organic frameworks (HOFs) are considered as potential choice for future energy storage systems due to their adjustable chemistry, environmental benignity, and cost-effectiveness. However, the electrochemical reaction mechanisms of the HOFs remain elusive. Herein, we demonstrate the site-selective electrochemical storage of alkaline metal ions (Li⁺, Na⁺, and K⁺) in porphyrin-based hydrogen-bonded organic framework (PFC-72-Co). Through systematic experimental and theoretical investigations, three active sites are identified, namely, carbonyl site (site 1), porphyrin site (site 2), and interstitial site (site 3). The carbonyl functional group can accommodate all alkaline metal ions (Li⁺, Na⁺, K⁺), whereas the porphyrin and interstitial sites are selective only for Li⁺ ions. As a result, the monomer Co-TCPP, with its abundant active sites, is a promising anode material for potassium-ion batteries, hosting 7 K⁺ ions and delivering a reversible capacity of 247.6 mAh g^-1. In contrast, the PFC-72-Co framework, owing to its low solubility in the electrolyte, serves as a stable anode for lithium-ion batteries, exhibiting ultrahigh cycling stability of over 10,000 cycles. This work provides new understanding of the electrochemical reaction mechanisms of organic materials for alkaline metal-ion batteries.

Silver nanoparticles (Ag-NPs) are widely used as antibacterial materials and accumulate in sewage sludge as silver sulfide nanoparticles (Ag₂S-NPs) after wastewater treatment. Composting using black soldier fly (BSF) is an effective method for treating sewage sludge. This study investigated the impact of Ag/Ag₂S-NP-containing sludge on greenhouse gas emissions during BSF composting. The results indicated that BSF significantly increased N₂O and CH₄ emissions during composting. However, the addition of 5 mg/kg or 100 mg/kg of Ag/Ag₂S-NPs significantly reduced N₂O emissions by 51.7-86.1 %, and CH₄ emissions by 44.3-92.9 %. Quantitative analysis of genes in the sludge revealed that the inhibition of hao and norB genes, and the enhancement of nosZ genes were critical factors reducing N₂O emissions. For CH₄, inhibition of methanogenic genes (mcrA) and the enhancement of methane oxidation genes (pmoA) were the primary mechanisms by which Ag₂S-NPs reduced CH₄ emissions. Based on X-ray absorption spectroscopy (XAS) and single-particle ICP-MS (spICP-MS), Ag was retained predominantly as Ag₂S throughout, with small fractions converting to AgCl in the larval gut, and particles exhibited modest size reduction. Further metagenomic analysis revealed Ag-driven alterations in BSF gut microbiota, including decreased microbial diversity, and suppressed denitrification and methanogenesis pathways. This study offers an economical and effective method to reduce greenhouse gas emissions during sewage sludge treatment using BSF composting when Ag₂S-NPs are present.

The efficiency of two-phase anaerobic digestion hinges on the acidogenic phase, where acidogenic off-gas generates autogenic pressure that alters the physicochemical environment and may affect microbial activity, pathways, and intermediates. However, its mechanistic role under solid-state conditions remains unclear. To address this knowledge gaps, we investigated the effects of autogenic pressure on solid-state food waste acidogenesis, focusing on soluble microbial product (SMP) formation and the associated metabolic responses at the molecular level. Autogenic pressure enhanced acidogenic decomposition, increasing SMP yields from 365.3 ± 10.5 g COD/kg VS_added to 407.1 ± 7.3 g COD/kg VS_added. It initially promoted lactate production, followed by enhanced conversion of lactate to butyrate and acetate functioning by Megasphaera. Metagenomic and metabolite analyses revealed that autogenic pressure increased the abundance of functional genes associated with homoacetogenesis and butyrate synthesis. Incubation experiments further confirmed that acetate, stimulated by autogenic pressure, played a key role in driving the reverse β-oxidation pathway while suppressing the acrylate pathway during lactate conversion. As a result, butyrate production increased by 25 %, while propionate decreased by 43 %. These findings provide new insights into how SMP-producing microbial communities respond to autogenic pressure and demonstrate the potential of self-regulation to enhance product yield and process controllability. This strategy advances sustainable solid waste management and promotes the development of circular bioeconomy.