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Amazonian anthrosols are renowned for their high fertility and dark color, properties primarily attributed to the abundance of condensed aromatic carbon (ConAC) in the soil organic matter. ConAC, commonly referred to as black carbon, play a key role in the stability and nutrient retention of these soils. However, the processes governing the formation of ConAC and its transformation into oxygenated derivatives remain poorly understood. In this study, we used multiple analytical platforms to investigate the chemistry of ConAC-rich humic acids (HA) extracted from Terra Mulata de Indio, a type of Amazonian anthrosol. The results reveal that ConAC are predominantly nonprotonated and consist of approximately 4−10 condensed rings. These structures exhibit varying degrees of oxygenation (1−24 oxygen atoms), suggesting that they are produced through oxidative processes. Approximately 20% of ConAC contain nitrogen atoms, referred to as ConAN (condensed aromatic nitrogen), which are part of either heterocyclic ring systems (commonly termed black nitrogen) or present as amine functional groups. As a result, we conclude that HA in Amazonian anthrosols contain polycyclic N-containing aromatic acids (PolyNARA), likely formed through combined charring of plant and animal biomass, abiotic nitrogen incorporation, and/or other soil processes. The mechanisms governing the formation, persistence, and transformation of PolyNARA in Amazonian anthrosols warrant further investigation, particularly given their potential implications for global carbon and nitrogen biogeochemical cycling. 

Abstract Conventional topochemical photopolymerization reactions occur exclusively in precisely-engineered photoactive crystalline states, which often produces high-insoluble polymers. To mitigate this, here, we report the mechanoactivation of photostable styryldipyrylium-based monomers, which results in their amorphization-enabled solid-state photopolymerization and produces soluble and processable amorphous polymers. A combination of solid-state nuclear magnetic resonance, X-ray diffraction, and absorption/fluorescence spectroscopy reveals the crucial role of a mechanically-disordered monomer phase in yielding polymers via photo-induced [2 + 2] cycloaddition reaction. Hence, mechanoactivation and amorphization can expand the scope of topochemical polymerization conditions to open up opportunities for generating polymers that are otherwise difficult to synthesize and analyze. 

A mechanistic investigation of molecular solar thermal energy release by solid-state cycloreversion of dianthracenes to anthracenes reveals the integral roles of chemical and physical transformations of molecules towards the total energy release. 

Abstract Boron trifluoride (BF₃) is a highly corrosive gas widely used in industry. Confining BF₃in porous materials ensures safe and convenient handling and prevents its degradation. Hence, it is highly desired to develop porous materials with high adsorption capacity, high stability, and resistance to BF₃corrosion. Herein, we designed and synthesized a Lewis basic single‐crystalline hydrogen‐bond crosslinked organic framework (H_COF‐50) for BF₃storage and its application in catalysis. Specifically, we introduced self‐complementaryortho‐alkoxy‐benzamide hydrogen‐bonding moieties to direct the formation of highly organized hydrogen‐bonded networks, which were subsequently photo‐crosslinked to generate H_COFs. The H_COF‐50 features Lewis basic thioether linkages and electron‐rich pore surfaces for BF₃uptake. As a result, H_COF‐50 shows a record‐high 14.2 mmol/g BF₃uptake capacity. The BF₃uptake in H_COF‐50 is reversible, leading to the slow release of BF₃. We leveraged this property to reduce the undesirable chain transfer and termination in the cationic polymerization of vinyl ethers. Polymers with higher molecular weights and lower polydispersity were generated compared to those synthesized using BF₃ ⋅ Et₂O. The elucidation of the structure–property relationship, as provided by the single‐crystal X‐ray structures, combined with the high BF₃uptake capacity and controlled sorption, highlights the molecular understanding of framework‐guest interactions in addressing contemporary challenges. 

A comprehensive 13 C nuclear magnetic resonance (NMR) approach for characterizing the location of chain ends of polyethers and polyesters, at the crystallite surface or in the amorphous layers, is presented. The OH chain ends of polyoxymethylene are labeled with 13 COO-acetyl groups and their dynamics probed by 13 C NMR with chemical shift anisotropy (CSA) recoupling. At least three-quarters of the chain ends are not mobile dangling cilia but are immobilized, exhibiting a powder pattern characteristic of the crystalline environment and fast CSA dephasing. The location and clustering of the immobilized chain ends are analyzed by spin diffusion. Fast 1 H spin diffusion from the amorphous regions shows confinement of chain ends to the crystallite surface, corroborated by fast 13 C spin exchange between chain ends. These observations confirm the principle of avoidance of density anomalies, which requires that chains terminate at the crystallite surface to stay out of the crowded interfacial layer.