ABSTRACT In the quest for efficient molecular catalysts for the hydrogen evolution reaction (HER), we report two cobalt(II) complexes bearing redox‐innocent and non‐innocent ligands. Two cobalt(II) complexes, [Co( L1 )Cl](ClO 4 ) ( 1 ) and [Co( L2 )(bpy)Cl](ClO 4 ) ( 2 ) (where L1 = 1‐(1‐methyl‐1H‐benzo[d]imidazol‐2‐yl)‐N,N‐bis(pyridin‐2‐ylmethyl)methanamine and L2 = 4 / ‐(anthracen‐9‐yl)‐2,2 / :6 / ,2 // ‐terpyridine) bearing redox inactive ( L1 ) as well as redox active ligand ( L2 ) systems were synthesized and thoroughly characterized by different spectroscopic and analytical tools. The molecular structures of complexes were confirmed using single‐crystal x‐ray diffraction. Their electrocatalytic hydrogen evolution studies were performed using acetic acid as an external proton source, and the generated hydrogen was quantified by gas chromatography with faradaic efficiency above 90%. Theoretical calculations have also been performed to support the experimental results and develop the mechanism at an atomistic level. It was observed that ligand modification can shift the Co(II)/(I) redox potential significantly, but this will not assure the generation of a cobalt‐hydride active intermediate at less negative potentials, as the formed low valent cobalt species could be less nucleophilic to directly attack H + from acetic acid. Post‐catalytic analyses were also performed to check the integrity of metal complexes as molecular catalysts.

Dual-atom catalysts (DACs) have emerged as promising candidates for various chemical transformations with excellent atom utilization and synergistic effects between adjacent metal sites. However, their controlled synthesis and detailed understanding of cooperative effects remain challenging. Here, we design Ag-Cu dual sites embedded in a g-C3N4 matrix (AgCu-CN) through a supramolecular self-assembly approach followed by thermal polymerization by pyrolysis. The atomically engineered catalyst exhibits a hydrogen evolution rate of 2126 µmol g-1 h-1, and an apparent quantum yield (AQY) of 20% at 400 nm, surpassing the other reported metal-N coordinated photocatalysts. X-ray absorption spectroscopy (XAS) confirms the atomic-level dispersion and coordination with the g-C3N4 framework of the Ag and Cu single atomic sites. Comprehensive characterizations including transient absorption (TA) spectroscopy and theoretical calculations based on density functional theory demonstrate that the presence of the two metal centers broadens the photoabsorption range, enhances density of states close to the Fermi level. Thus we posit that it promotes excited state electron transfer and charge separation, and facilitate H2O activation by directing electron migration toward the protonation site, thereby stabilizing the H* intermediate, a crucial step in hydrogen evolution reaction. The catalysts developed in this study exhibit excellent activity, stability, and cost-effectiveness, highlighting their strong potential for practical clean hydrogen production.

The void space of a metal-organic framework (MOF) can, in principle, be chemically programmed to engage selectively with guest molecules through geometric complementarity or specific non-covalent interactions. In this work we have demonstrated that such molecular recognition can be turned on in an otherwise nonselective porous MOF thin film by the deliberate installation of a charge trap chromophore. The chromophore, naphthaleneimide, formed a donor-acceptor complex with the MOF linker 4,4'-anthracene-9,10-diylbis(ethyne-2,1-diyl))dibenzoic acid (AEBA), when positioned at the nanopore surface. This spatial design rendered nanochannels with high sensitivity to the polarity of adsorbed guest molecules. Photoexcitation of this engineered MOF film on a patterned Au-electrode device promoted efficient exciton dissociation, yielding enhanced photocurrents whose magnitude, dark to light switching ratio and rise dynamics depend decisively on the adsorbed molecules. Notably, these distinct electrical signatures disappeared in the unmodified MOF film, underscoring the essential role of charge-trap design. This strategy provides a generalizable route to activate molecular recognition in nonspecific MOF platforms and heralds new opportunities for sensitive, programmable chemical sensing.

Grain boundaries (GBs) introduce unique structural and electronic heterogeneity in metals. These planar defects display undercoordinated atoms, distorted lattices and localized charge variations that profoundly influence catalytic processes. To assess the structural diversity of the surfaces exposed due to the presence of GBs, we developed a methodology that assigns a numerical measure of similarity between different surfaces. Using this framework, we selected eight gold GB structures that represent the most diverse geometries with favorable formation energies. To gauge how active each site is towards chemical reactions, we specifically studied the chemisorption of CO2 on a handful of selected sites and compared with the top site of a Au(111) surface. Neutral Au surfaces do not spontaneously chemisorb CO2, so excess surface charge was systematically applied to probe charge dependent activation. The change in energy difference between the physisorbed and chemisorbed states (∆Epc) as a function of surface charge density was taken as a parameter to probe the activity of the various top sites across the selected surfaces. Interestingly, there are low energy surfaces where some sites are more active than the reference top site of a Au(111) plane while others are less reactive. We further discovered a predictive chemical marker, partial atomic charge on the C atom, that correlates strongly with the ordering of ∆Epc under charge neutral conditions to enable rapid screening of active sites.

Ambient processing of organic semiconductors (OSCs) is crucial for scalable, cost-effective device manufacturing; however, it is often hindered by uncontrolled, unintentional interactions with oxygen. Mitigating such interactions and even leveraging them to enhance the optoelectronic properties of OSCs will further enhance the application of OSCs in low-cost, printable optoelectronic devices. Here, we developed two organic salt additives to modify the electronic properties of OSCs during thin-film preparation under ambient conditions. The addition of these bespoke salts to commonly used hole-transport materials (HTMs) significantly increases the conductivity and charge-carrier mobility of the OSCs. We elucidate here the underlying mechanism responsible for this improvement: the cationic component of the salts scavenges superoxide species generated during ambient processing and storage, while the anionic component reduces electronic trap densities in the OSC films. Owing to the generality of this mechanism, these additives offer a new and versatile strategy for enhancing the optoelectronic performance of organic semiconductors processed in ambient conditions.

Does light or heat play a seminal role in photo-rechargeable batteries? This study unravels the effects of light in the exciton formation and separation processes in a photocathode, leading to the charging or de-intercalation of Li+ ions in a lithium-ion battery. Light induced oxidation of Ti3+ to Ti4+ in the Lix(TiS2-TiO2) heterostructure cathode is shown here, while heating does not elicit such changes. With the aid of photogenerated electrons at the cathode, the de-lithiated Li+ ions from Lix(TiS2-TiO2) get intercalated in the graphite anode during the photocharging process. Direct or passive heating leads to the degradation of the cathode electrolyte interface (CEI), instigating enhancement in open circuit potential. In contrast, photocharging leaves the organic electrolytes and CEI unaffected. Hence energy efficient photo-electrochemical energy systems can be built by carefully isolating the effects of heat and light in solar radiation, as dictated by this study.

Finding stable binding sites of alkali metal ions on two-dimensional transition metal dichalcogenides (TMDs) is crucial for predicting and engineering the usage of these materials in batteries and optoelectronic devices. However, conventional approaches using density functional theory (DFT), where the energies of the intercalated layers are analyzed upon sequential addition of each ion, face significant challenges due to the substantial number of calculations involved. Alternatively, one can employ point charge analysis to predict the most favorable binding sites. In this study, we first show that such analyses cannot be extended to arbitrary concentration of intercalated ions. Furthermore, we compare the DFT derived energies and electrostatic energies based on nearest neighbors and show that while it improves upon the direct point charge predictions, the correlation is still limited to certain concentrations. Finally, we develop a machine learning-based ranking model employing the electrostatic energies as predictive features. This model demonstrates high accuracy in predicting the ordering of the energies of different binding sites across a diverse range of alkali metal ion concentrations and types, as well as various sizes and types of TMDs.

Impaired neuronal functions and cell death within ailments such as neurodegenerative Parkinson's disease pose significant challenges due to their complex pathophysiology and limited treatment options. In this landscape, innovative materials with unique physicochemical properties that ameliorate the debilitated neuronal functions are critically required. Neuronal functions rely on the conduction of nerve impulses, a process that can be effectively targeted using advanced materials that exhibit conducive properties essential for modulating neural activity. For their semiconductor characteristics, combined with well-suited biocompatibility, graphitic carbon nitride (g-C3N4) nanosheets provide promising avenues for such neurotherapeutic applications. Our multidisciplinary study investigates the potential of g-C3N4 nanosheets in promoting neuronal differentiation and network formation across in vitro and in vivo systems. SH-SY5Y cells exposed to g-C3N4 demonstrated enhanced neuronal differentiation and neuritic outgrowth over a chronic 21-days period, accompanied by an increased intracellular Ca2+ influx, pivotal for dopamine biosynthesis, as evidenced by the upregulated expression of vesicular monoamine transporter 2 (VMAT2), aromatic l-amino acid decarboxylase (AADC), and tyrosine hydroxylase (TH) genes. Utilizing transgenic Caenorhabditis elegans model expressing human α-synuclein, we observed the neuroprotective potential of g-C3N4, as evidenced by reduced protein aggregation and improved dopaminergic functions. In the pursuit of exploring the mechanism of g-C3N4-induced neuronal stimulation, the semiconducting nature of g-C3N4 came forth, which was further validated using theoretical (in silico) models. These models demonstrated an increase in the chemical potential of the material upon the application of electrical biases. Studying Ca2+ channel inhibition, we also observed that phenotypic and molecular effects were the outcomes of the stimulation caused due to the presence of g-C3N4 nanosheets. Our findings, supported by experimental and in silico studies, suggest that g-C3N4 nanosheets can effectively modulate neuronal behavior through their semiconducting properties, offering promising avenues for therapeutic interventions in neurodegenerative diseases.

Graphene oxide has been extensively employed as an additive in several nanocomposites to enhance their mechanical stability even though its Young's modulus is significantly smaller than that of pristine graphene. In the past decade, various chemical functionalizations have been attempted to enhance the mechanical strength of graphene oxide. In this work, we analyze the atomic contributions to the Young's modulus (YM) of graphene oxide with relevant models to decouple the role of the defects and the oxygen functionalities. Based on our analysis we show that (1) the presence of defects is more important than the oxygen groups for reducing the YM and (2) the defect atoms provide negative contribution to the YM at low defect densities. The latter novel observation can be exploited, in principle, to perform selective substitution of the defect atoms to increase the YM of graphene oxide while keeping other functional groups in the non-defect region intact for further functionalization, if required. In the proof of concept example, 75% of the enhancement of the YM obtained upon substitution of the oxygen functionalities with two hydrogen atoms, in silico, can be accomplished by displacing just 10% of the oxygen atoms that are exclusive to the defects.

The interactions between water molecules and gold surfaces are central to biocompatibility and electrocatalysis, yet their fundamental nature remains highly controversial. Recent findings indicating a molecular-level hydrophobicity have challenged the classical view of gold being hydrophilic. Using surface-specific spectroscopy and ab initio simulations, we demonstrate that gold is neither hydrophobic nor hydrophilic in the classical sense, but exhibits strong electronic interactions with water, resulting in an orientation-dependent electronic heterogeneity. These findings are important for the properties of metal-aqueous interfaces with broad applications.

Nature employs water as the reaction medium for enzymatic redox transformations, taking advantage of its unique physicochemical properties to precisely regulate reaction kinetics, selectivity, and proton-coupled electron transfer. In a biomimetic endeavour, using a newly developed non-heme (Et4N)[MnV(O)(Ph,Me-bTAML)] complex, we report a water-induced, enzyme-like rate acceleration in hydrogen atom transfer (HAT) reactivity with various substrates possessing BDEs of 67-78 kcal mol-1. In acetonitrile, the reactivity is sluggish, but switching to water - particularly beyond 85% content - results in a dramatic rate enhancement, peaking in pure water with up to a 20 000-fold increase. This effect occurs without any structural changes or addition of external additives. Mechanistic insights suggest that water stabilises the minimum energy crossing point (MECP) more effectively than acetonitrile through enhanced electrostatics and hydrogen bonding in transition-state energetics. This is the first demonstration of a non-heme Mn(V)-oxo complex mimicking enzymatic rate enhancement solely via solvent modulation. The work highlights water's active role in driving selective, efficient, and green oxidation chemistry, unlocking new potential in bioinspired catalysis.

Molecular diffusion in porous solids (metal-organic and covalent organic frameworks, zeolites) can be regulated by engineering the chemical environment of the nanochannels. Selective chemical interactions between the nanochannel surface and diffusing molecules enable discrimination at the molecular level, a feature critical for the development of high-performance chemical separation membranes. A major challenge, however, is to concurrently achieve rapid molecular diffusion and high selectivity, as these attributes exhibit an intrinsic trade-off. In this communication we introduce a de novo methodology exploring the rotational dynamics of the nanochannel chemical components and realize simultaneous enhancement of both diffusion and selectivity for aliphatic chemical isomers (branched hexanes). The methodology utilizes crystalline metal-organic framework thin film architecture akin to membrane structures, supported by a comprehensive experimental and simulation framework to achieve the dual objectives effectively.

Zeolitic imidazolate framework-8 (ZIF-8), constructed from Zn2+ ions and 2-methylimidazole (mIm) linkers, is widely recognized for its excellent thermal and chemical stability, making it a strong candidate for chemical separation and heterogeneous catalysis. In this study, we report a new crystalline phase of functionalized ZIF-8 featuring a spatially graded distribution of chemical functionalities. This anisotropic functionalization is achieved via a vapor-phase process applied to a ZIF-8 monolithic film. Anisotropic diffusion of a reactive linker-imidazole-2-carboxaldehyde (CHO-Im)-into the ZIF-8 monolith results in a gradient incorporation of CHO-Im, yielding a ZIF-8-CHO monolith. Spatial anisotropy of the CHO functional groups is confirmed through X-ray diffraction, scanning electron microscopy, and vibrational spectroscopy. To demonstrate its potential, we fabricated an anodic aluminium oxide-supported membrane and highlighted its enhanced gas permselectivity compared to pristine membranes.

Understanding the solvation structures of OH- and H3O+ at metal interfaces is crucial for developing efficient electrochemical devices. In this paper, we present a detailed investigation of the solvation structures of OH- and H3O+ near gold electrodes under alkaline and acidic aqueous conditions, using ab initio molecular dynamics simulations at controlled surface charge density conditions. Our findings reveal that the adsorption tendencies of OH- and H3O+ are strongly influenced by the oscillating net atomic charge of water normal to the electrified interface in concert with the distinct solvation patterns of these charge defects. While OH- preferentially adsorbs onto the gold surface within the first water layer, the positive net atomic charge restricts the closest approach of H3O+ to beyond the first water layer. We unveil resting and active states that support charge transfer processes at the gold/water interface, which critically involve Au atoms in a unique Grotthuss-like mechanism.

Understanding metal-water interfaces is instrumental in developing electrochemical cells for energy conversion. In this Letter, we quantify the relative contribution of the metal surface and the solvent molecules to the electronic component of the interfacial dipole moment enabled by an implementation of partially occupied Wannier functions that allows us to treat interfacial water in contact with metallic surfaces. Our calculations show that the contribution of the solvent is of overriding importance and that it mostly originates from specific deformation of the water lone pairs very close to the metal surface.

Gas permselective membranes are inherently constrained by a trade-off between permeability and selectivity. Overcoming this limitation is key to enabling broader industrial adoption, and advanced porous materials-particularly metal-organic framework (MOF)-has emerged as promising candidate. Yet, to truly rival established separation technologies such as, distillation, pressure swing adsorption and chemisorption, innovative design strategies remain essential. Traditionally, efforts to surpass the trade-off have focused on regulating porosity, pore architecture, pore surface chemical functionality, and macroscopic transport pathways (particle morphology). These modifications are achieved either through bottom-up synthetic approaches or by employing external stimuli such as light, pressure, or electric fields. In this work, we introduce a photochargeable membrane that enhances gas permselectivity through precise, molecule-specific interactions-without altering the underlying porous architecture. This is achieved by incorporating a nanoporous MOF, constructed from redox-active organic ligands, as filler in a mixed matrix membrane. Upon photoexcitation, ligand-ligand charge separation yields stable pore surface charges, facilitating selective interactions with quadrupolar CO2. This specific interaction enhances CO2/N2 and CO2/CH4 permselectivity, surpassing the Robeson upper bound. The proof-of-concept can be explored for mixed and high purity gas feed preparation.

MoS2 monolayers (MS) having magnetic impurities as dopants can bring about time-reversal asymmetry and hence room temperature magnetism. Here, we demonstrated the synthesis of Cr substitutionally doped (∼1%) MS (CrMS) along with its vanadium-doped MS counterpart (VMS) and investigated their suitability for valleytronics by studies based on chirality-selective photoluminescence, time-resolved transient absorption spectroscopy, and spin Hall effect of light (SHEL). While VMS showed room temperature valley splitting, no such shift was observed in CrMS although with their expected similarity. Density-functional-theory-based electronic structure calculations indicate a Cr-induced flat band below the Fermi level, even at ∼0.5 atom % doping, which masks the splitting in the energies of the K-point valleys. This finding is in tune with the experimental studies while in contrast to the theoretical and experimental data of VMS. Hence, this study establishes band valley tunabilities of MoS2, and SHEL as a powerful tool for valley polarization studies.

A dual-catalytic strategy has been developed to access conjugated enyne benzofurans via an unprecedented unsymmetrical homocoupling of ortho-iodophenyl propargyl ethers. An earth-abundant Cu-(II)/Fe-(III) dual-catalyst system enables high chemoselectivity and efficiency. Detailed mechanistic investigations, including control experiments and comprehensive density functional theory (DFT) studies, reveal that the reaction proceeds through in situ generation of Cu-(I) species, followed by an annulation event. The transformation culminates in a unique three-carbon homologation, involving a second propargyl unit and facilitated by the Fe-(III) cocatalyst. A broad array of enyne benzofuran derivatives bearing diverse functional groups was synthesized in up to 90% isolated yield. The synthetic practicality and wide applicability of this methodology are further demonstrated through gram-scale synthesis and postfunctionalization of the enyne moiety.

Layered semiconductor materials such as transition metal dichalcogenides are known to undergo phase transition from the semiconducting (H) to a metallic/quasi-metallic ( T/T^' ) phase upon ion intercalation, thus changing their physical and electronic properties. Initially, based on a computational set-up that treats both phases (H and T’) on the same footing and allows extraction of electron density from lithium intercalated MoS2, we predict that the phase transition can be delayed in MoS2 with almost 1.5 times the amount of cation accommodation while the layers are in contact with another material (MoO3), forming a type-II heterostructure. This important theoretical prediction is then validated via in situ Raman spectroscopy and electron transport measurements, where the concentration of the intercalated Li-ions is controlled by applying an external voltage. The ability to store more Li-ions in the same phase extends the scope of these heterostructures in light driven processes/devices, e.g. photocatalysis, and light-chargeable batteries.