Browse Articles

Pulse-Driven Paired Electrosynthesis of Formamide via Redox-Tuned Intermediate Management

Abstract Renewable electricity-driven electrocatalytic systems hold promise for the sustainable formamide (HCONH2) synthesis. However, a major bottleneck remains the low Faradaic efficiency (FE) and overall electron utilization inherent to current unipolar C–N coupling strategies, where substantial electron consumption at the counter electrode severely limits system efficiency. Here, we propose a redox-tuned paradigm (Ared+ Boxi→ C) through a pulsed paired electrosynthesis strategy. Using an atomically ordered CuPd catalyst with CH3OH and NO2– as feedstocks in an undivided cell, HCONH2 is simultaneously produced at both electrodes under optimized pulse conditions with alternating change in potential periodically (Ea = 1.3 V, ta = 10 s; Ec = −0.7 V, tc = 10 s). This system achieves an FE of 85.6% for HCONH2 at a current density of 81.5 mA cm–2, with a yield of 263.3 μmol·h–1·cm–2. The FE is higher than those reported to date. Mechanism studies reveal that pulsed operation creates a periodically switching cathode/anode environment. This enables the ordered CuPd catalyst to function sequentially as a reduction site (converting NO2– to *NH3) during cathodic pulses and as a co-oxidation site (converting *NH3 to *NH2 along with CH3OH to *HCOH) during anodic pulses, thereby driving efficient C–N bond coupling to form HCONH2. Techno-economic analysis further confirmed the significant industrial potential of this strategy in the future renewable energy market.

Efficient Synthesis of N-Bridged Annulenes

Abstract The most commonly encountered aromatic structure is the benzenoid ring, which is observed in a wide variety of pharmaceuticals and organic materials. However, studies on nonbenzenoid conjugated polyene aromatic molecules remain scarce, largely due to synthetic challenges and inherent angle strain. Herein, we report an unprecedented single-copper relay dual-catalyzed cascade sequence for the efficient construction of a unique aromatic N-bridged [10]annulene (NBA) framework (also called cycl[3,2,2]azine), in which a copper-catalyzed 10π electrocyclization is involved. To gain insight into the reaction mechanism, a series of control experiments and density functional theory calculations were conducted. The developed reaction exhibits broad functional-group tolerance and can be extended to different classes of 14π components. Significantly, the resulting NBA compounds display strong fluorescence with full-color tunability. Therefore, these innovations not only deepen our understanding of the aromaticity of nonbenzenoid systems but also highlight the potential of metal-catalyzed electrocyclization in synthetic chemistry.

Identifying Disordered Intermediates in the Reaction of Cu3– <i>x</i> P and Dibenzyl Diselenide to form Cu3PSe4 Nanoparticles

Abstract Developing a detailed understanding of ternary nanoparticle (TNP) formation is essential for their optimized rational synthesis and development of synthetic routes for new TNPs. Herein, we explore the reaction of Cu3–xP and dibenzyl diselenide (Bn2Se2) to form colloidal Cu3PSe4 TNPs. Temperature-resolved X-ray scattering (XRD and PDF), electron microscopy (TEM and STEM), and spectroscopy (EDS, EELS, XPS, and MAS NMR) reveal that Cu3–xP reacts by surface coordination of Se leading to fragmentation followed by rearrangement to Cu–Se binary phases, during which all obvious crystalline P-containing phases disappear via XRD. However, partially oxidized P in solid phases was observed using STEM-EDS and XPS, in which P is found to preform P–Se bonds prior to Cu3PSe4 formation. Using a combination of 31P MAS NMR and PDF analysis obtained from synchrotron total scattering data, P–Se bonds in [PSe4]3– tetrahedral building blocks were identified within intermediate Cu–Se phases containing P cation substitution (PCu), denoted (Cu,P)–Se, that assemble into Cu3PSe4. We hypothesize that these intermediate compounds with their substoichiometric, vacancy-rich structures and significant Cu disorder are important for accessing Cu3PSe4─offering a new insight into complex TNP syntheses. We summarize our findings by writing plausible pseudoelementary steps (PESteps) in which the Cu3–xP precursor converts to smaller fragments of Cu–Se phases containing P en route to the final Cu3PSe4 product. Additional interesting aspects of this system include the use of Bn2Se2 as a readily monitorable probe for the reaction and the Se–P bond formation that facilitates Cu–P bond cleavage in an overall 8-electron redox reaction involving P3– and 4 Se0. The results obtained lay the groundwork for future mechanistic investigations, notably kinetics studies working from the PESteps aimed ultimately at the rational design and synthesis of complex ternary pnictogen chalcogenide nanoparticles.

Reaction Medium as an Architect of Nanocrystal Superlattices

Abstract Nanocrystal superlattices are commonly formed by changing concentration, solvent conditions, or particle surface chemistry. Although effective, these approaches alter multiple contributions to the interparticle potential simultaneously, making it difficult to isolate the interactions responsible for ordering or to control assembly in chemically complex environments. Here, we show that oligomeric species present in a nanocrystal reaction medium drive superlattice formation through a depletion mechanism. Using PbTe nanocrystals as a model system, we identify Pb–oleate oligomers in the crude reaction mixture, characterize their solution structure, and quantify their contribution to the interparticle potential, establishing depletion as the dominant short-range interaction governing spontaneous body-centered cubic superlattice formation. We then confirm the depletion origin of ordering by showing that varying depletant concentration predictably shifts the order–disorder boundary and produces a thermally reversible transition between dispersed and ordered states ─ behavior that is inconsistent with van der Waals or ligand-mediated mechanisms but is a direct consequence of depletion control. Having established and validated the mechanism, we demonstrate that the same depletion framework can be deliberately activated in purified dispersions and transferred across nanocrystal systems of different composition and shape, including anisotropic and binary assemblies. These results establish precursor-derived depletion as a general and chemically grounded mechanism for nanocrystal superlattice formation, and show that collective ordering can be programmed through the surrounding medium rather than through particle surface modification.

Ultrabright Near-Infrared Lead-Free Perovskite Light-Emitting Diodes with Negligible Efficiency Roll-Off

Abstract Lead-free halide perovskite semiconductors show great promise for light-emitting diodes (LEDs), benefiting from tunable optoelectronic properties and solution processability. However, their practical applications in high-current-density LEDs are fundamentally constrained by severe efficiency roll-off, primarily caused by nonradiative recombination and carrier-induced structural instabilities. In this study, we introduce a molecular N,N′-diphenylthiourea (DPTA)-engineered tin perovskite semiconductor (CsSnI3) that achieves a photoluminescence quantum efficiency (PLQE) of 36% at a carrier concentration of 1018 cm–3. Our approach enables precise control over the charge-carrier concentration and lattice growth. High-resolution transmission electron microscopy further demonstrates that the uniform local strain distribution in the doped films enhances carrier wave-function overlap, leading to a substantial boost in PLQE. Leveraging the enhanced optoelectronic properties of DPTA-treated CsSnI3, we fabricate near-infrared LEDs that exhibit an external quantum efficiency (EQE) of 13.4% and an unprecedented peak radiance of 1248 W sr–1 m–2, with minimal efficiency roll-off even at high current densities exceeding 3500 mA cm–2 in pulse-mode operation. This work introduces a new material-doping strategy for lead-free perovskites, demonstrating their potential for high-power optoelectronic applications and advancing the feasibility of electrically pumped perovskite laser diodes.

Highly Dynamic Yet Stable Polyketimine Networks with Closed-Loop Recyclability and Topological Programmability

Abstract Closed-loop recycling via depolymerization has emerged as a promising strategy to mitigate plastic pollution. Ideal recyclable polymer networks should feature highly dynamic bonds that depolymerize efficiently into monomers/oligomers. However, this intrinsic bond lability inevitably introduces a critical trade-off, as it typically undermines the material’s stability. In this work, we design a polyketimine network that can be closed-loop recycled under mild conditions, without the need for consumable reagents or catalysts, while retaining robust mechanical properties during use. At the molecular level, hindered ketimine bonds remain sufficiently labile to depolymerize back to the designed oligomers, due to the steric hindrance from the ketone and amine reactants. At the network level, however, hydrophobic phases block water ingress, effectively “locking” the network and preserving mechanical performance even under harsh conditions (85 °C, 85% relative humidity, 48 h). When recycling is desired, a compatible organic solvent disrupts these hydrophobic phases, allowing water to penetrate the network and trigger depolymerization. Consequently, depolymerization and repolymerization cycles can be conducted using only easily recoverable water and solvents under mild conditions. By leveraging this dynamic chemistry, the synthesized polymers can be disassembled and reassembled into diverse network topologies, corresponding to a Young’s modulus that spans 6 orders of magnitude. Our work demonstrates that intrinsically labile dynamic bonds can be harnessed to build stable materials with tunable properties, offering a versatile platform for next-generation closed-loop recyclable polymers.

Chain Length Dependence of Chemically Controlled Reactions in Polymerization

Abstract Chemically controlled reactions in polymerization processes are traditionally assumed to have chain-length-independent rate coefficients. However, this work challenges that assumption by using multiscale modeling to demonstrate that chemically controlled polymer–polymer reactions can exhibit significant chain length effects. Taking reversible addition–fragmentation chain transfer (RAFT) polymerization as a case study, we compare the chain length convergence of the reaction entropy for two processes: the addition of a growing polymer radical to a simultaneously growing polymeric RAFT agent, and the analogous reaction involving a low molecular weight RAFT agent. While the latter reaches equilibrium within 10 monomer additions, the former shows delayed convergence, with effects persisting to degrees of polymerization (DP) of 100 or more. A similar trend was observed in the Diels–Alder step-growth polymerization, where rapid convergence occurred when one chain length was fixed and short, but markedly slower convergence was observed when both reacting chain lengths increased simultaneously. These results reveal that entropy contributions, which scale logarithmically with chain length, lead to significant chain length dependence in the equilibrium constants (Keq). Because these effects arise from fundamental entropic considerations rather than specific features of the reacting species, they are expected to manifest broadly in the kinetics and thermodynamics of other chemically controlled polymer–polymer reactions. Our findings provide a mechanistic basis for resolving discrepancies in experimental estimates of fragmentation rate coefficients, shedding light on debate surrounding rate retardation in RAFT systems. More broadly, this work underscores the importance of chain length effects in the kinetics and thermodynamics of chemically controlled polymer–polymer reactions.

Retraction of “Nanoscale Covalent Organic Framework with Staggered Stacking of Phthalocyanines for Mitochondria-Targeted Photodynamic Therapy”

Deactivating Emission in Azulene via Solvent-Induced (Anti)Aromaticity

Abstract Anti-Kasha emission is a coveted feature in optoelectronics, with promise in areas such as imaging, sensing, and the production of white-light LEDs via dual-photon emission. Despite being a rare feature in organic systems, anti-Kasha emission is readily observed in the deceptively simple molecule azulene, which possesses two bright singlet states in the UV–visible spectrum and readily emits from the S2 state. With dominant anti-Kasha emission and decades of synthetic study, azulene is a perfect candidate for novel material fabrication; however, large gaps persist in understanding the photophysics of even the simple parent compound. These range from competing, experimentally unverified models of azulene reactivity and aromaticity to the unexplained deactivation of anti-Kasha emission in a host of azulene derivatives. Herein, we use fluorescence and transient absorption spectroscopies to explore the detailed solvent dependence of azulene photophysics. We discover a tunable reduction in the S2 lifetime via weak complexation with aromatic solvents. Interestingly, our results are independent of polarity, highlighting the primacy of peripherally delocalized 10-π Hückel aromaticity over zwitterionic character. When the dipolar character is enhanced through chemical functionalization, we observe even greater sensitivity to solvent aromaticity and more rapid quenching, revealing the role of conical intersections in azulenes with zwitterionic excited states. Overall, this work provides essential mechanistic insight into the photophysics of azulene and reveals a simple new approach to control the excited-state aromaticity and anti-Kasha emission in this class of materials.

Perthionitrite-Induced Persulfidation in Binuclear Cobalt(II) Complexes

Abstract Persulfidation of sulfhydryl functional group (-SH) in protein and nonprotein thiols is a physiologically important process and generally involves the reduction of a partially oxidized sulfur by a fully reduced sulfur. In the present work, two dicobalt(II)-nitrito complexes, [Co2(PhBIMP)(μ-NO2)(DMF)]2+ (2) and [Co2(PhBIMP)(μ-NO2)2]1+ (3), have been demonstrated to react with RC(O)SH (R = Me, Ph) to generate the persulfidated complexes, [Co2(PhBIMP)(μ-SSC(O)R)]2+ (R = Me, 5a; Ph, 5b) in high yields (65–72%) along with nitric oxide (71–80%). Characterization of all the products and intermediates by structural and spectroscopic methods, and comparison of the results with those obtained from control experiments, established the generation of [Co2(PhBIMP)(μ-SC(O)R)(MeCN)]2+ (R = Me, 4a; Ph, 4b) and perthionitrite (SSNO–) in the reactions of 2/3 with RC(O)SH, followed by persulfidation of the coordinated thiocarboxylate (RC(O)S–) in 4a and 4b by the in situ generated SSNO– to produce the persulfidated complexes, 5a and 5b, respectively. The present work thus demonstrates, for the first time, that SSNO–, a physiologically relevant S/N-crosstalk species, can effectively mediate the persulfidation of sulfhydryl functional groups and may implicate a similar, but hitherto unknown, role of SSNO– in biological persulfidation processes.

Cycloparaphenylene-Derived Porous Organic Cylinders

Abstract Cycloparaphenylenes, with their distinctive radial conjugation and high macrocyclic rigidity, hold significant yet underexplored potential for the development of novel porous structures. We report the rational design and facile synthesis of three porous organic cylinders (POCys). Through dynamic boronate ester linkages, the coaxial covalent assembly of two catechol-functionalized cycloparaphenylenes could generate cylindrical scaffolds featuring large intrinsic cavities with interconnected channel networks. One of the POCys exhibits high porosity, showing a Brunauer–Emmett–Teller surface area of 1241 m2·g–1 and excellent gas adsorption capability. This work demonstrates the promise of cycloparaphenylene derivatives as a molecular platform for designing functional porous organic architectures.

Semiclassical Theory of Stepped Electrodes and Step Bunching

Abstract Atomic-scale steps markedly influence electrochemical activity and stability and exhibit structural instability under electrochemical conditions. Yet the microscopic mechanisms that cause these behaviors remain largely unclear. Herein, we study the microstructure and thermodynamics of the electrical double layer at stepped electrodes, using the semiclassical density-potential functional theory. The theory captures trends observed in experiments regarding the differential capacitance and the potential of zero free charge (PZFC) with step density for stepped Au and Ag . Departing from the case of flat electrodes, the PZFC deviates from the potential of minimum capacitance at stepped electrodes, necessitating local PZFCs to describe heterogeneous surface charging conditions. Furthermore, linking step-induced PZFC shifts to changes of the surface tension, the theory predicts that step bunching is thermodynamically driven at more positive electrode potentials and sensitive to the electrolyte composition.

Unlocking Anion Reduction of Lithium Perchlorate via Electrochemically Coupled Oxygen Atom Transfer

Abstract The growing demand for high energy density electrochemical energy storage necessitates energy vectors that maximize the number of electrons transferred per formula unit of active material. Herein, we introduce electrochemically coupled oxygen atom transfer (OAT) as a new paradigm to harness the energy of p-block oxoanions in a Li–metal solid-state battery. Using carbon-supported Fe nanoparticles in a dual role of OAT catalyst and conversion-type cathode active material, we demonstrate the eight-electron anion reduction of ClO4– at &amp;gt;50% conversion, delivering a capacity of 1150 mA h g–1 and an energy density of 1950 W h kg–1. We further demonstrate strategies to enhance the energy density at the electrode level, establishing a foundation for oxoanion-based anion redox in battery systems.

Coulombic Metal–Organic Frameworks Assembled from π-Stacked Organic Nodes and Polyoxometalate Inorganic Linkers

Abstract Metal–organic frameworks (MOFs) are typically constructed by forming coordination bonds between inorganic nodes and organic linkers. Here we present an alternative framework chemistry that does not rely on coordination bonding but instead exploits proton-transfer-facilitated Coulombic and hydrogen-bonding interactions. Protonation of basic amine molecules by acidic Keggin-type polyoxometalates (POMs) generates complementary organic cations and inorganic anions that rapidly self-assemble into crystalline frameworks at room temperature upon simple solution mixing. Solvent acidity modulates proton transfer and charge balance, thereby controlling amine–POM stoichiometry and packing modes and driving a structural evolution from π-stacked organic arrays (CouMOF-1) to a MOF-like node–linker network (CouMOF-2) and ultimately to a continuous POM-stacked phase (CouMOF-3). The intermediate phase, CouMOF-2, comprises a primitive cubic (pcu) net in which π-stacked organic molecules serve as 6-connected supramolecular organic nodes bridged by 2-connected POM clusters, producing a MOF-like topology without coordination bonding and representing a rare inversion of the conventional inorganic-node/organic-linker architecture of MOFs. These materials exhibit different sulfide oxidation activities and selectivities, highlighting solvent-controlled assembly as a route to tuning structure–function relationships. This assembly strategy extends to diverse amine monomers and polyoxometalates, and the synthetic simplicity together with the large chemical space of amine–POM combinations highlights organic–inorganic acid–base assembly as a versatile route to crystalline ionic frameworks that use nondirectional Coulombic interactions to generate ordered framework architectures, without resorting to coordination chemistry.

Photoactive Heteropore Covalent Metal–Organic Frameworks for CO2 Photoreduction

Abstract Metal–organic frameworks (MOFs) as a class of promising photocatalysts have been used for photocatalytic CO2 reduction reaction (CO2RR). Although many strategies have been developed for enhancing the photocatalytic activities, constructing photoactive heteropore MOFs for CO2RR remains largely unexplored. Herein, we report the synthesis of two two-dimensional (2D) copper cyclic trinuclear unit (Cu-CTU)-based heteropore covalent MOFs (CMOFs) and two homopore analogues. Interestingly, the heteropore CMOFs showed two times higher CO2 uptake than their homopore analogues. Moreover, the introduction of photosensitive units into heteropore CMOFs promoted light harvesting as well as charge separation, achieving a CO generation rate of 3548 μmol g–1 h–1 with 94.7% selectivity and an apparent quantum yield (AQY) of 6.78% at 420 nm in the presence of [Ru(bpy)3]Cl2. Notably, the photoactive heteropore CMOFs delivered high photocatalytic activity under diluted CO2 and natural sunlight conditions. Our work demonstrated that incorporation of heteropore structures and photosensitive units into MOFs can synergistically enhance photocatalytic CO2RR performance.

The Effect of Nanoparticle Structure on the Thermodynamics and Kinetics of Proton-Coupled Electron Transfer Reactions to V2O5

Abstract Proton-coupled electron transfers (PCETs) to metal oxides are key reactions for sustainable catalytic and energy storage processes. The factors that control PCET reactions on metal oxides are, however, not well understood, with the effect of particle morphology/surface faceting on the thermodynamics and kinetics of PCET being essentially untested. We measured the thermodynamics and kinetics of PCET from CpCr(CO)3H to five V2O5 samples of varying morphologies/surface faceting. Their nanostructures were assessed by Rietveld refinement accounting for preferred crystallite orientation, giving a semiquantitative measurement of surface faceting. PCET to V2O5 occurs via proton insertion-coupled electron transfer (PICET), where H· diffuses into the bulk of the particle. The thermodynamics of PICET are controlled by particle structure, with nonequilibrium morphologies requiring structural rearrangement during PICET. The kinetics of PICET are controlled by the rate of H· diffusion into the bulk, with diffusion along the interconnected V2O5 layers being 10x faster than between the layers. Samples with hindered H· diffusion also show low activity in the oxidation of methanol, demonstrating that diffusion of H· into the bulk occurs during catalysis. This work demonstrates that particle morphology is critical for PCET reactions to anisotropic metal oxides and must be considered when examining their reactivity.

Photocatalytic Conversion of Aminocyclopropanes to γ-Lactams by Sequential Ring-Expansion and Peripheral Diversification

Abstract Rings underpin pharmaceuticals, agrochemicals, and materials, driving renewed interest in skeletal ring expansion. Current skeletal ring expansion strategies mainly focus on single-atom insertion or rearrangement; reliable methods for multiple single-atom insertion and peripheral diversification of saturated small rings are lacking. Herein, we report a general and efficient photocatalytic system directly converting aminocyclopropanes to γ-lactams via sequential C-/N-single-atom [n + 2] ring-expansion and peripheral diversification. The system accomplishes both γ-lactam formation and subsequent diversification at the γ-position via six distinct bond-forming reactions across hundreds of synthetic examples under predictable reaction conditions. Experimental and computational studies converge on photoredox-mediated radical pathways.

Enzyme-Activatable Fluorogenic Probes: Design Strategies, Biomedical Applications, and Future Perspectives

Abstract Enzymes are pivotal regulators of cellular metabolism and organismal homeostasis, and their dysregulation is often associated with the onset and progression of disease. Therefore, accurate monitoring of the real activities of target enzymes is essential for deciphering biological mechanisms and gaining pathological insight. Through decades of iterative refinement, a diverse repertoire of enzyme-activatable fluorogenic probes (EAFPs) have been developed, enabling the capture of aberrant enzyme dynamics with high spatiotemporal resolution and multifunctional biosensing capabilities. In this context, we highlight the current state-of-the-art EAFPs, spanning fundamental design principles to proof-of-concept applications. First, the molecular engineering, sensing mechanisms, and design strategies of EAFPs are introduced. Next, a wide range of cutting-edge probes for imaging and sensing target enzyme(s) are presented, with emphasis on structural features, recognition mechanisms, and biomedical applications. Representative examples in biomarker imaging, disease diagnosis, drug screening, and therapeutic testing are highlighted to illustrate both the design principles and practical utility. Finally, the existing challenges and future trajectories for EAFPs in specific application scenarios are discussed. The insights presented here will inspire and accelerate the development of high-performance multifunctional EAFPs for both fundamental and translational research.

Controlling the Double Layer of Platinum by Selective Passivation of Step Sites Using Adatom Modification

Abstract The structure of the electric double layer at platinum electrodes remains incompletely understood, even for the model Pt(111)/HClO4 interface, which deviates significantly from Gouy–Chapman–Stern theory. While Pt(111) exhibits a true double-layer window (0.40–0.60 VRHE) that enables direct measurement of the double-layer capacitance, stepped Pt surfaces do not because hydrogen and/or hydroxyl species adsorb at low-coordinated step sites across the entire potential range. We previously showed that hydroxyl adsorption on (110)-steps is potential-independent within this nominal double-layer window, leading to decreasing capacitance with increasing (110)-step density due to suppression of the step Helmholtz capacitance. In contrast, (100)-steps exhibit potential-dependent hydroxyl adsorption that introduces a substantial pseudocapacitive contribution and increases capacitance with step density. Here, we selectively passivate Pt step sites by depositing Au* and Ag* adatoms. We find that Au*step-modification suppresses step-specific adsorption, restoring predominantly electrostatic behavior for (100)-type stepped Pt surfaces and reversing the capacitance trends observed for the bare stepped surfaces. In contrast, Ag*step-modification introduced an additional chemical contribution, manifested as substantially increased capacitance and enhanced CO oxidation activity due to adsorption of oxophilic species on Ag*. These results demonstrate that Pt step-site chemistry, and consequently the electrical double-layer structure and electrocatalytic activities, can be tuned and probed to a remarkable degree of controllability through selective adatom modification.

Interpretable Machine Learning Unveils Hydroxyl/Amino Synergy and Guides Discovery of Optimal MOF Photocatalysts for Hydrogen Evolution

Abstract Metal–organic frameworks (MOFs) are premier platforms for photocatalytic hydrogen evolution (PHER), yet navigating their multidimensional parameter space typically relies on inefficient trial-and-error approach. While machine learning (ML) can accelerate discovery, it is often hindered by ″black-box″ predictions that lack mechanistic transparency and experimental validation. Herein, we establish an interpretable ML-to-experimental framework for rational MOF engineering. By training a CatBoost model on a curated database and employing SHapley Additive Explanations (SHAP), we deconstructed the hierarchical influence of ligand motifs on catalytic activity. This revealed the cooperative effect of hydroxyl and amino dual functionalization, which optimizes the electronic landscape through balanced bandgap dynamics and hard–soft acid–base (HSAB) matching. Guided by these insights, we synthesized benzophenanthrene-based mixed-ligand MOFs. The champion catalyst achieved a peak HER rate of 73.7 mmol g–1 h–1─without external photosensitizers or cocatalysts─exhibiting a 4.18% deviation from algorithmic predictions and a 15.8% enhancement over the top of the data set. This work develops a high-performance photocatalytic system and provides a generalizable, interpretable paradigm for data-driven discovery of advanced energy materials.