Researchers at Imperial and Exeter investigated why ultrafast optical switching in indium tin oxide reaches saturation – and identified a distinct high-intensity regime not captured by the conventional two-temperature model

Covalent organic framework (COF) membranes with high crystallinity hold great promise in precise molecular separation, but often suffer from the intercrystalline defects and thus poor membrane-formation ability. This study reports a sequential imine exchange strategy to fabricate highly crystalline, defect-free COF membranes for precise molecular separation. Two functional amines (aromatic and aliphatic amines) are employed in highly reversible imine exchange reaction to separately conduct crystallization and defect remedy processes according to their different energy gaps. Aromatic amine, which serves as COF framework building unit, undergoes the first-step imine exchange for high crystallinity because of its lower energy gap. Afterward, the hyperbranched aliphatic amine with abundant amino groups undergoes the second-step imine exchange, affording the tight connections between adjacent crystals and the excellent membrane-formation ability. Accordingly, the COF membrane exhibits high permeance (344 L m⁻² h⁻¹ bar⁻¹ for water, 462 L m⁻² h⁻¹ bar⁻¹ for methanol) and rejection (> 99.9% for Congo red and Alcian blue). Meanwhile, the membrane is endowed with an ultrahigh separation factor (> 528) for mixed dye aqueous solutions and large-scale processability (> 290 cm²). This work offers a new strategy to fabricate highly crystalline and defect-free COF membranes, revealing their large potential in diverse practical applications.

Achieving precise and on-demand steering of the oxygen reduction reaction (ORR) pathway between the efficient 4e⁻ route to H₂O and the valuable 2e⁻ route to H₂O₂ remains a pivotal challenge in electrocatalysis. Herein, we address this challenge by designing a bioinspired molecular magnetic field-responsive catalyst (MMFR-C) via magnetic single-atom-anchored Salen-based covalent organic frameworks (MSA-Salen COFs) onto magnetic nanoparticles (single/multi-domain Fe₃O₄). Mimicking cytochrome c oxidase, the MMFR-C employs MSA-Salen COFs as an ordered proton-transfer channel and well-defined N₂-M-O₂ moieties as enzymatic O₂ activation sites, with Fe₃O₄ providing a built-in magnetic field for remote regulation of the active-site electronic structure. The bioinspired MMFR-C exhibits switchable ORR pathways. Relative to the pristine Co-Salen COF (26% H₂O₂ selectivity, n = 3.48), the MMFR-C integrated with a single-domain Fe₃O₄ exhibits a remarkably enhanced H₂O₂ selectivity of 63.9% (n = 2.72), while that with a multi-domain Fe₃O₄ diverts the ORR pathway toward the 4e⁻ route (n = 3.67). (i) We elucidate that the uniform magnetic field from the single-domain Fe₃O₄ in MMFR-C favors orbital hybridization between its active N₂-M-O₂ moieties and the *OOH intermediate, with moderate *OOH adsorption suppressing O–O scission and thus steering ORR selectivity toward H₂O₂. (ii) In contrast, the enhanced specific magnetism from its multi-domain Fe₃O₄ core optimizes the d-band center of MMFR-C’s active sites, stabilizes triplet O₂ adsorption, and reduces spin-forbidden transition barriers, thereby facilitating O–O cleavage and diverting its ORR pathway to the 4e⁻ route.

To settle inherent irreversible phase transition and motivate re-dissolution of deposited “dead” MnO₂ without acid and redox mediator addition, we introduced atomic-dispersed Co atoms with high-spin state into layered MnO₂, denoted as Co–MnO₂, via an in situ topological phase transformation strategy, thereby unlocking reversible multi-electron transfer chemistry for superb Zn–Mn batteries. Specifically, atomic-distributed Co atoms within Co–MnO₂ effectively modulate [MnO₆] octahedral symmetry and reduce Co–O bond covalency along with enhanced lattice oxygen activity. Based on this, high-spin Co (t_2g⁴e_g²) greatly mitigates the Jahn–Teller distortion as well as promotes electrolytic MnO₂ deposited onto the cathode surface completely converted from adsorbed Mn²⁺ for inhibited “Mn dendrites”, achieving reversible MnO₂/Mn³⁺ and electrolytic MnO₂/Mn²⁺ reactions with highly thermodynamical favorability. Benefiting from the “two-step, three-electron” mechanism triggered by high-spin Co, Zn//Co–MnO₂ battery delivers an outstanding capacity of 658 mAh g^–1 and ultra-long lifespan over 15,000 cycles. This work reveals the critical role of transition-metal spin state modulation for energy-dense and durable Zn-MnO₂ batteries with reversible multi-electron storage mechanisms.

Nitrogen fertilizers are essential for crop production, but much of the nitrogen applied to agricultural soils is lost before plants can use it. These losses not only waste valuable nutrients but also contribute to environmental pollution and greenhouse gas emissions. Scientists have now discovered that adding manganese to biochar can help soil retain more nitrogen by strengthening a natural microbial process.

Agricultural residues, wood waste, and other discarded plant materials could become valuable resources for cleaner energy and environmental technologies. Yet producing consistently high-performing carbon materials from these renewable resources remains a major challenge. Scientists now highlight a critical reason: the properties of the original biomass can determine how well the final carbon material performs.