Stabilizing active Snδ+ sites of Sn-Ce-Ox solid solution catalyst for durable acidic CO2 electroreduction

Mixed metal oxides, such as ZnZrOx, have attracted considerable interest as CO2 hydrogenation to methanol catalysts due to their high methanol selectivity (> 70%) and catalytic stability at elevated reaction temperatures (> 300°C). In this work, we introduce a novel ZnHfOx catalyst that exceeds the intrinsic methanol formation rate of the reference ZnZrOx at a Zn content of 20 mol% (rMeOH,20ZnZrOx = 0.59 molMeOH(molcath)-1, rMeOH,20ZnHfOx = 0.68 molMeOH(molcath)-1). Remarkably and in contrast to ZnZrOx, the ZnHfOx-based catalysts exhibit a high methanol selectivity (> 70%) up to Zn contents of 99.5 mol% despite the segregation of ZnO. Operando spectroscopy, in combination with computational analysis, identifies the Zn-VO-Hf motif as the active site for methanol formation that proceeds via the formate-methoxy pathway. Such active sites are not only present in solid solution-type ZnHfOx catalysts (≤ 35 mol% Zn), but also in the form of isolated HfOx clusters on segregated ZnO surfaces (for high Zn contents of > 35 mol%), explaining the high selectivity (and activity) over a wide range of Zn contents.

Chiral-angle-controlled synthesis of carbon nanotubes (CNTs) remains a central challenge, particularly in continuous growth processes such as floating catalyst chemical vapor deposition (FC-CVD), where high productivity is attractive but tight structural control is difficult to achieve. In this study, a mist-based FC-CVD platform is established for continuous single-walled CNT (SWCNT) growth, enabling systematic modulation of the chiral-angle distribution through expanded catalyst-precursor design. By introducing ultrasonic aerosol-mist delivery, volatility constraints in precursor feeding are relaxed, allowing co-delivery of a non-volatile W precursor (ammonium metatungstate) with ferrocene to create a W-containing Fe-based catalyst system under atmospheric-pressure FC-CVD conditions. This catalyst system promotes pronounced near-armchair enrichment, shifting the CNT chiral-angle distribution away from achiral limits while narrowing the distribution compared with W-free synthesis. Analysis based on a theoretical abundance expression for CNT growth on solid catalysts is consistent with a stabilization-based interpretation, in which W-containing species may increase the effective thermal/structural stability of Fe-based catalyst nanoparticles and the catalyst-CNT interface, thereby strengthening chiral-angle selectivity. Furthermore, tuning the carbon supply reveals an optimal regime for maximizing near-armchair enrichment, whereas supply-limited and overfed conditions broaden the distribution through distinct kinetic pathways. These results provide a practical route toward scalable chiral-angle-controlled CNT synthesis in continuous FC-CVD.

Developing solid catalysts to overcome multiple environmental challenges through a single system is an increasingly significant objective in sustainable chemistry. Here, we have synthesized a robust two-dimensional copper phosphonate framework (Cu-Pz) using 1-hydroxyethane1,1-diphosphonic acid (HEDP) and pyrazine, which enables photocatalytic dye degradation, solvent-free CO2 fixation and C-C bond formation heterogeneously. Owing to the variable Cu2+ coordination environments, Lewis-acidic Cu sites, and phosphonate-derived basic oxygen atoms, the framework activates both H2O2 and dissolved oxygen under blue-light irradiation, generating •OH and •O2- species through a synergistic photo-Fenton-like mechanism. This dual reactive oxygen species (ROS) pathway enables rapid degradation of a bulky diazo organic dye, i.e., Congo Red (CR), demonstrating efficient operation under narrow-band, low-energy light. We have observed 93% degradation of CR after 60 min of visible-light irradiation. As pseudo-first-order reaction kinetics are observed in photocatalytic degradation, we achieve a 0.04 min-1 rate constant for the degradation of CR. Beyond photocatalysis, the hybrid acid-base environment permits solvent-free Knoevenagel condensation and efficient CO2 cycloaddition with epoxides, underscoring the material's inherent catalytic flexibility. We achieve 98% conversion with a 327 Turnover Number (TON) for CO2 fixation employing 0.03 mmol of catalyst and 98% conversion with a 274 TON for the Knoevenagel condensation with 0.025 mmol catalyst loading. The framework's exceptional structural integrity and recyclability are maintained throughout all reactions, highlighting its robustness and usefulness. As a key step toward sustainable catalytic advancement, this multifunctional copper phosphonate catalyst provides an integrated, environmentally friendly method for CO2 utilization, organic synthesis, and dye degradation.

Oxygen vacancy-mediated photothermal CO2 methanation over Ni/Ce-Zr solid solution catalysts.

Polyoxometalates (POMs) are bifunctional acid-redox catalysts with significant potential for biomass valorization. Herein, we investigate the heterogeneous catalytic studies of an immobilized 4,4'-bipyridine Cu-substituted Keggin POM, (4,4'-bpyH2)2(4,4'-bpyH)-[PCuW11O39]·H2O (Bp-PCuW11), anchored onto graphene oxide (GO) via ball milling. The Bp-PCuW11/GO nanohybrid proved to be an efficient solid acid heterogeneous catalyst for starch hydrolysis, resulting in the formation of glucose as a variable compound. Under optimized hydrothermal conditions, a superior catalytic performance was achieved with 92% starch conversion, 82% glucose yields, and excellent selectivity of 95%, coupled with over five recyclability runs. The Density functional theory (DFT) simulation revealed that the enhanced performance is attributed to the synergistic acid-redox behavior of PCuW11 and GO, which enables efficient proton transfer and improved substrate accessibility. This work provides new insights into the rational design of POM-carbon hybrid catalysts for sustainable biomass valorization and other environmentally relevant catalytic transformations.

Ionic liquids (ILs) are known to promote the catalytic hydrogenation of CO2 to formic acid, in particular by shifting the reaction equilibrium through formic acid stabilization. While a broad range of ILs-formic acid interactions has been described, proposed, and discussed in pure IL systems, the molecular basis for such stabilizing effects is not yet fully understood. Fundamental insights are desired for practically relevant solid catalysts such as those made from supported ionic liquid phases (SILPs). Herein, we apply solid-state nuclear magnetic resonance (NMR) spectroscopy to probe interactions between formic acid and four selected catalysts comprising ruthenium nanoparticles (NPs) immobilized on SiO2-based support materials including SILPs (Ru@SILPs). As evidenced by 1H transverse relaxation times and the efficiency of 1H-13C polarization transfers, a reduction in molecular motion of formic acid is observed upon its impregnation on Ru@SILPs with guanidinium- or imidazolium-based IL-type molecular modifiers compared to the surfaces with alkyl modifiers or pristine SiO2. The NMR spectra reveal spatial proximities between formic acid and the cationic surface modifiers pointing to weak chemical interactions with the cationic modifiers. Our findings provide deeper mechanistic insights into the stabilizing role of SILPs for formic acid, with implications for the synthesis of formic acid from CO2 hydrogenation.

ABSTRACT Electrocatalysis plays a pivotal role in renewable energy conversion and environmental governance, enabling key processes such as water splitting, CO 2 reduction, and nitrogen fixation. Despite significant advancements, precise regulation of catalytic performance at the atomic and molecular levels remains a challenge. This review presents a cross‐scale, dynamic analytical framework that integrates active site engineering with interfacial microenvironment regulation, spanning inorganic solid catalysts and molecular catalysts. We summarize recent progress in structural and electronic modulation of active sites, interface microenvironment engineering, catalyst stability enhancement, molecular dispersion control, and complex reaction pathway elucidation. We highlight innovative strategies from inorganic catalysts—including single‐atom catalysts with tailored coordination environments, multi‐metal synergistic sites, defect engineering, and dynamic reconstruction—to molecular catalysts with precisely controlled dispersion states, electronic structures, and conformational dynamics. The review also discusses the roles of advanced in situ characterization and machine learning in resolving dynamic reaction mechanisms and accelerating catalyst design. Finally, we identify key challenges such as precise active site regulation, real‐time monitoring of dynamic interfacial processes, and long‐term stability, and outline future directions, including atomically precise catalyst design and dynamic interface regulation. These insights lay the foundation for developing next‐generation electrocatalysts with high activity, selectivity, and durability for sustainable energy applications.

Conventional biochar-based solid base catalysts often suffer from cumbersome preparation procedures and pore blockage during the loading of active components. To overcome these limitations, we developed an in situ construction strategy to fabricate hierarchically porous solid-base catalysts via cross-linking and carbonization of alkali lignin. Using alkali lignin as the carbon precursor, a soft-template-assisted cross-linking system enables the simultaneous formation of a hierarchical carbon framework and in situ generation of basic active sites through one-step pyrolysis under alkaline conditions. The physicochemical properties of the catalysts, including specific surface area, pore structure, and surface basicity, are effectively tuned by adjusting the carbonization temperature (600–800 °C). The optimized catalyst, KLPF-800, exhibits a high specific surface area of 309 m2·g−1 and a well-developed hierarchical pore architecture, delivering excellent catalytic performance in aqueous-phase glucose isomerization. A fructose yield of 33.21% is achieved at 120 °C within 20 min. This work provides a feasible strategy for valorizing lignin and designing efficient heterogeneous base catalysts.

The spatial distribution of active sites governs the behavior of solid catalysts, yet how it shapes local temperature gradients and thereby affects catalytic performance remains poorly understood. Here, using the industrially important propane dehydrogenation (PDH) over CoOx confined in silicalite-1 (S-1) zeolites as a model system, we show that catalytic activity and stability are enhanced when CoOx is peripherally confined near the crystal surface (CoOx@S-1-M), rather than uniformly distributed throughout the zeolite (CoOx@S-1-U), which differs from conventional catalyst design strategies that emphasize uniform active-site dispersion for stability. To uncover the origin of this behavior, we probe the local temperatures of CoOx clusters by developing in situ high-resolution microscopic Raman thermometry. CoOx@S-1-U exhibits a pronounced core-to-edge thermal gradient, with the temperature difference exceeding 17 °C, whereas CoOx@S-1-M maintains a much more uniform temperature distribution, with the difference limited to 8 °C. CoOx@S-1-M also exhibits higher propane conversion and stability, consistent with this thermal behavior. Mechanistic analysis reveals that the smaller temperature drop at CoOx clusters in CoOx@S-1-M enhances propylene desorption and suppresses side reactions and coke formation, deviating from the commonly accepted view that higher temperatures generally promote coke growth. These findings establish a direct link between active-site spatial location and catalytic performance through microscale temperature gradients at active clusters, providing a new perspective for the rational design of supported metal catalysts.

This review highlights recent advancements (2021-2025) in the one-pot multicomponent synthesis of 2-amino-5-oxo-4-phenyl-4H,5H-pyrano[3,2-c][1]benzopyran-3-carbonitriles, a class of biologically significant heterocycles with diverse pharmacological properties. The methodologies are categorized based on the type of catalyst used, including deep eutectic solvent-based catalysts, ionic liquid-based catalysts, nanocatalysts, heterogeneous hybrid solid green catalysts, homogeneous base catalysts like piperidine, agro-waste extract, organo-salt catalyst and tertiary base surfactant. These catalytic systems have demonstrated improvements in reaction efficiency, environmental sustainability, and product yields. By organizing these developments, the review provides a valuable resource for guiding future research in green and efficient heterocyclic synthesis.

The rising global need for sustainable energy has driven the exploration of efficient and cost-effective pathways for producing biodiesel from renewable resources. This work presents the development of an enhanced solid catalyst (NES9-3) derived from a synergistic blend of eggshells and sardine scales (ES). Unlike conventional eggshell-derived calcium oxide (CaO) catalysts, which often suffer from rapid deactivation due to leaching, the incorporation of sardine scale-derived hydroxyapatite (HAP) introduces a synergistic effect, providing improved structural stability and partial resistance to catalyst deactivation. The 1:1 ES mixture was first thermally treated at 900 °C for 3 h to obtain the ES9-3 catalyst, which served as a reference catalyst. A subsequent hydration-dehydration-recalcination process was employed to produce the NES9-3 catalyst, aiming to generate a more porous structure with increased surface area and enhanced catalytic activity. Structural characterization using thermogravimetric analysis (TGA), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS), and Brunauer-Emmett-Teller (BET) analysis confirmed significant phase transformations, enhanced textural properties, and reduced crystallite size following the modification treatment. The transesterification of waste frying oil (WFO) was optimized using response surface methodology. Under the optimized conditions (2.97 wt% catalyst, 12.35:1 methanol-to-oil molar ratio, and 3.02 h reaction time), the NES9-3 catalyst achieved a biodiesel yield of 93.72% with a conversion efficiency of 97.29%, as confirmed by 1H nuclear magnetic resonance (1H NMR). In contrast, ES9-3 exhibited a lower yield of 85.8% under identical conditions and required a longer reaction time and higher methanol consumption to achieve an 89% yield. Gas chromatography-mass spectrometry (GC-MS) analysis confirmed the formation of fatty acid methyl esters (FAMEs), and the resulting biodiesel complied with ASTM D6751 and EN 14214 fuel standards. This study demonstrates that coupling CaO with hydroxyapatite, followed by hydration-dehydration modification, provides a strategy to partially mitigate catalyst deactivation and improve catalytic efficiency, offering a sustainable and economically viable approach for biodiesel production within a circular bioeconomy framework.

We have employed density functional theory (DFT) calculations to explore the catalytic potential of scandium nitride (Sc₂N) MXenes for CO2 capture and hydrogenation to methane. The Sc₂N surface exhibits a strong affinity for CO₂ with an adsorption energy of -3.627 eV, surpassing values reported for other MXenes, such as Ti₂N and V₂N, and even outperforming conventional catalysts like Pt(111). Charge density difference and COHP analyses reveal significant back-donation from Sc d-orbitals to the antibonding orbitals of CO2, resulting in the formation of activated CO2δ- species. AIMD simulations confirm the thermal stability of Sc₂N under ambient conditions. The hydrogenation pathway to CH₄ proceeds via eight elementary steps, with the CH₂OH + H → CH₃OH reaction identified as the rate-determining step due to its high activation barrier (2.916 eV). Sc₂N effectively stabilizes key intermediates, such as COOH, HCOOH and CH₂OH, and facilitates H₂ dissociation with moderate energy requirements. Compared with other MXenes, Sc₂N shows superior ability to stabilize intermediates, particularly HCOOH, which plays a crucial role in the conversion pathway. However, large negative adsorption energies for H and O atoms suggest potential surface poisoning, which may limit catalytic turnover unless regeneration strategies are implemented. These findings highlight Sc₂N MXenes as robust and efficient materials for CO2 capture and conversion, although further optimization is necessary for sustained catalytic performance. This article is part of the theme issue 'Surfaces, interfaces and heterogeneous catalysis'.

ABSTRACT The esterification reaction of n‐propyl alcohol with n‐propionic acid using Indion 140 solid catalyst is carried out in an isothermal batch reactor to produce n‐propyl propionate and water. The reaction temperature is maintained in the range of 333–353 K and the catalyst loading varies from 0.01 to 0.03 g/cc. The mole ratio of n‐propionic acid and n‐propyl alcohol varies from 1:1 to 1:6. The influence of various parameters such as temperature, catalyst loading, initial reactant molar ratio, catalyst size, and agitation speed on the reaction rate are investigated. From the experimental results, it is observed that the reaction is kinetic controlled rather than mass transfer controlled. A second‐order pseudo‐homogeneous kinetic rate equation is used to fit the experimental data. The activation energies and forward reaction rate constants are obtained from the Arrhenius plot. The comparison of the simulation results with the experimental data indicates the second‐order pseudo‐homogeneous non‐ideal kinetic model better describes the behavior of the esterification reaction. The rate equation thus developed in this work can be used in modeling and design of catalytic distillation involving esterification of propionic acid with propanol.

ABSTRACTPiezo‐photocatalysis synergistically integrates the features of piezocatalysis and photocatalysis, offering promising applications in environmental remediation, energy conversion, and biomedical therapy. Herein, we introduce modularly designed solid molecular catalysts (SMCs) comprised of metal‐free, polyaromatic, two‐dimensional polymers which offer an unprecedented level of control over piezopolarization—and consequently, piezo‐photocatalysis—through the rational design of structural motifs (diphenylpyridine or terpyridine) and backbone functionalities (methyl group, aliphatic amine antenna, or aromatic pyrrole ring). We demonstrate that piezopolarization, induced by ultrasound across a wide frequency range (35 kHz to 2.6 MHz), enables highly efficient sono‐piezo‐photocatalytic hydrogen peroxide production. The SMC AP5 featuring the terpyridine motif and pyrrole functionalization is the most active metal‐free piezo‐photocatalyst for hydrogen peroxide production under ambient conditions. Furthermore, the instantaneous on/off‐switchability of the sono‐piezo‐photocatalysts is shown, underscoring their potential for applications requiring spatiotemporal control over catalytic activity.

The redox mechanisms of silica-supported Ni particles were investigated using their in situ X-ray absorption fine structure, providing mechanistic insights into partially reduced NiO and partially oxidized metallic Ni. The results of surface oxidation of partially reduced NiO particles at room temperature revealed that the surface was not fully covered with metallic Ni and that metallic Ni had also formed within the particle interior. During NiO particle reduction, the process initiates at specific surface sites, and before the metallic Ni phase fully covers the surface, O2- ions are expelled from the particle. Conversely, the oxidation of metallic Ni particles progresses inward from the surface, with an accompanying increase in the thickness of the NiO layer that forms upon O2 exposure at room temperature. This mechanism is supported by observations that the reduction of a thin NiO shell on metallic Ni particles was completed below 200 °C, while reduction temperatures shifted to higher values as the NiO layer thickness increased. The distinct oxidation and reduction mechanisms are attributed to differences in the migration direction of O2- ions. During reduction, it is proposed that O2- ions within the particles migrate to the surface along the interface between the NiO phase and the metallic Ni phase. This study elucidates the detailed mechanism behind the redox interconversion between NiO and metallic Ni in solid catalyst particles.

ABSTRACT Palladium‐loaded phosphine polymers have been designed and used as solid molecular catalysts (SMCs) in telomerization reactions with isoprene and short alcohols. A novel tris‐(2‐methoxyphenyl)phosphine‐based polymer (pTOMPP), previously reported poly triphenylphosphine (pTPP) as well as TPP‐based polymers with trigonal and tetragonal linkers were tested either pre‐loaded or in‐situ‐loaded. The novel polymer pTOMPP proved to be an excellent support material during in‐situ‐loading, outperforming triphenylphosphine based polymers. Surprisingly pre‐loaded SMCs resulted in significantly lower activity. XAS studies reveal that the enhanced activity of Pd/pTOMPP is due to the coordination sphere of Pd on the polymer showing a higher contribution of Pd‐P bonds forming, whereas XAS spectra of Pd/pTPP show a higher contribution of inactive Pd‐acac bonds. Especially pre‐loaded polymers show little Pd‐P interactions.

Production of glycerol butyl acetal as a biofuel additive via acetalization over a sulfonated solid acid carbon catalyst derived from bamboo charcoal

ABSTRACT Formic acid (FA) is considered to be a safe and convenient hydrogen source; however, achieving controlled and efficient FA dehydrogenation under mild conditions using stable solid catalysts remains a significant challenge. Pd‐based catalysts have been extensively studied due to their superior catalytic activity to other metal catalysts. Most researchers primarily attribute the activity of these catalysts to Pd 0 sites while recognizing the potential contributions of Pd 2+ species, and this merits further systematic investigation. In this study, Pd active species were innovatively loaded onto a defect‐rich g‐C 3 N 4 support engineered with biomass carbon, resulting in an exceptionally high Pd 2+ /Pd 0 ratio and enabling hydrogen evolution under nonreductive conditions. A strong interaction between the pyridinic nitrogen in the defect‐rich g‐C 3 N 4 support and Pd yields a high surface proportion of Pd 2+ species. Combined with in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) and density functional theory (DFT) calculations, HCOO* is identified as the key intermediate, predominantly adopting a bidentate adsorption mode on Pd n + sites. DFT calculations further reveal that HCOO* can undergo C–H bond cleavage on both Pd 0 and Pd n + sites. The high proportion of Pd 2+ is a critical factor underlying this system's enhanced catalytic activity and selectivity. Furthermore, the abundant defect sites on the support effectively prevent active Pd sites from aggregating. The resulting ultrasmall Pd particles further improve the electronic environment of the anchored Pd sites, enhancing the catalytic performance. The turnover frequency of the as‐prepared Pd/CN‐nutshell 5:1 catalyst reaches 5758 h −1 , substantially higher than most previously reported results.

Direct sulfonation of defatted sludge to prepare sulfonic acid solid catalysts for biodiesel production from sludge lipids