Atmospheric CO2 emissions are driving the climate crisis, prompting research into catalytic hydrogenation to produce value-added chemicals. Here, a ternary CoCuAl mixed-metal oxide catalyst derived from collapsed layered double hydroxides (LDHs) was developed for selective CO2 hydrogenation to C5+ hydrocarbons at 240 degrees C. Compared with LDH-derived CuAl (mainly yielded CO and methanol) and CoAl (mainly methane) catalysts, the ternary CoCuAl catalyst with a Co/(Co + Cu) ratio of 0.53 exhibited a remarkable shift in selectivity toward C5+ hydrocarbons (12.2%) due to synergy between Cu and Co. Cu promoted CO2-to-CO conversion via the reverse water-gas shift (RWGS) reaction, while Co enabled subsequent chain growth through Fischer-Tropsch synthesis (FTS). The low temperature of 240 degrees C was essential, as higher temperatures likely cause Cu-Co segregation and metallic Co particles that favor methanation over FTS. Importantly, the LDH-derived catalyst outperformed the conventional co-precipitated CoCuAl analog, delivering higher CO2 conversion (16.3% vs. 9.5%) and C5+ selectivity (12.2% vs. 5.0%), owing to superior metal dispersion from the LDH confinement effect. XPS confirmed strong Co-Cu interactions, and in-situ IR spectroscopy revealed key CO and formate intermediates. This work highlights the potential of LDH-derived mixed oxides for efficient CO2 valorization under mild conditions.

A chromium‐free catalyst for the high‐temperature water‐gas shift (HT‐WGS) reaction was developed using copper aluminate spinel synthesized via co‐precipitation. Powder X‐ray diffraction (PXRD) revealed that the material was amorphous when calcined at 500 °C but transformed into a well‐defined crystalline spinel structure at 800 °C. Scanning electron microscopy (SEM) and energy‐dispersive X‐ray spectroscopy (EDS) confirmed the formation of crystalline spinel morphology, which enhances thermal stability under HT‐WGS conditions. Hydrogen temperature‐programmed reduction (H 2 ‐TPR) showed a shift of the second copper reduction peak to a higher temperature, indicative of the robust nature of the spinel phase. Density functional theory (DFT) calculations further demonstrated that the spinel catalyst exhibits superior CO adsorption and H2O activation compared to its amorphous counterpart, thereby improving WGS activity. The catalyst calcined at 800 °C exhibited activity for both low‐ and high‐temperature WGS reactions; however, after H 2 reduction at 400 °C, it became selectively active for the HT‐WGS reaction. Long‐term stability testing confirmed excellent durability, maintaining an average CO conversion of 53.6% over 120 h at 400 °C, comparable to the 57% achieved by commercial Cr‐containing catalysts. These findings establish copper aluminate spinel as a robust, sustainable, and chromium‐free alternative for industrial HT‐WGS catalysis.

Deactivation of supported metal nanoparticles due to sintering is a key issue in industrial catalysts. We report an efficient, low-cost protocol for producing highly active and robust heterogeneous catalysts with low palladium loading (1.3%), high dispersion, and resistance to sintering. This is achieved using ethylenediamine (EN) as an inexpensive bidentate ligand for in situ complexation of Pd(II) ions in water, promoting stable impregnation and higher dispersion on a fumed silica support. Following EN decomposition in air at 225 degrees C for 48 h and subsequent hydrogen reduction, CO and H2 chemisorption revealed a marked increase in Pd dispersion, from 6% at molar ratio n = 0 to 30% at n = 4, plateauing at n = 4-6, for this set of Pd:nEN samples. These Pd nanoparticles showed excellent catalytic activity and stability for propylene hydrogenation at 250 degrees C. Consistent with the trend in dispersion, catalytic activity increased with increasing Pd:nEN ratio from n = 0 to 4, then plateaued at 93% for n = 4-6. Testing under higher space velocity confirmed that the catalyst retained both high activity and stability. In summary, EN could be an industrially applicable ligand that yields a fumed silica-supported Pd catalyst suitable for hydrogenation.

ABSTRACT Gold nanoclusters (AuNCs) have attracted attention as candidate photosensitizers because of their distinctive energy‐level characteristics. Coupling AuNCs with wide‐bandgap semiconductors such as solar irradiation by the semiconductor. Nevertheless, AuNCs readily aggregate and may deactivate under prolonged illumination, which limits sustained photoresponse. In this work, the cationic polymer polyethyleneimine (PEI) was introduced as a surface modifier to enhance the stability of AuNCs anchored on TiO 2 nanotube arrays. Owing to electrostatic interactions, the negatively charged AuNCs bind more firmly to the PEI‐treated TiO 2 surface, resulting in improved durability. In addition, the electronic structure of PEI promotes the separation of photogenerated charge carriers, leading to a marked increase in photocurrent density. Molecular dynamics simulations further indicate that PEI functionalization of TiO 2 substrates substantially improves the thermal stability of Au–GSH nanoparticles by facilitating heat dissipation and inhibiting sintering at elevated temperatures. Finally, AuNCs and PEI were coated with a Nafion layer to mitigate attack from aqueous electrolytes while preserving efficient electron transport pathways.

Ammonia cracking is a key reaction for hydrogen storage and release, offering a promising route toward a hydrogen economy. Herein, a robust silica-supported cobalt (Co) catalyst is developed using a histidine-assisted dispersion strategy to mitigate sintering. Histidine (His), a naturally occurring amino acid, is codissolved with the Co(II) precursor to produce uniformly dispersed Co nanoparticles on silica via incipient wetness impregnation (2, 6, and 10 wt %). The resulting particles exhibit sizes of similar to 2-3 nm, significantly smaller than those prepared without histidine. Thermogravimetric analysis confirms complete removal of histidine after treatment at 250 degrees C for 48 h. Synchrotron powder X-ray diffraction reveals that the histidine-assisted method suppresses Co3O4 formation, favoring smaller CoO species during the initial synthesis stage. H2 temperature-programmed reduction confirms the corresponding differences of Co3O4 and CoO in reducibility and further shows that histidine-assisted samples possess smaller nanoparticles. The 10 wt % Co-His/SiO2 catalyst demonstrates superior activity and stability in ammonia cracking at 500 degrees C, achieving 30.5% NH3 conversion compared to 13.5% for the nonhistidine-assisted counterpart. These findings confirm the use of histidine as a biodegradable ligand to conveniently prepare supported metal catalysts that are less prone to sintering and remain catalytically active in reactions critical to sustainability.

SSZ-13 zeolite membranes are promising for N2/CH4 gas separation owing to their unique pore architecture and superior stability. However, for the conventional secondary growth (CSG) of SSZ-13 membranes, the synthetic solution, particularly the organic template, is inefficiently utilized, causing unnecessarily high chemical consumption. To address this issue, this study introduces counter-diffusion crystallization (CDC) strategy that separates the organic template and silica source within and outside porous tube substrates to synthesize SSZ-13 membranes at the interface; this can reduce template usage by 92.5% for the same area of SSZ-13 membranes compared with the CSG method. Moreover, with the CDC strategy, the organic template can be recycled for membrane fabrication, further reducing raw material costs. The optimized SSZ-13 membranes show N2 permeance of 2.5 & times; 10- 8 mol m-2 s- 1 Pa- 1 and N2/CH4 selectivity of 15.7 at 298 K and 2 bar. Meanwhile, SSZ-13 membranes can maintain stable performance over one month of operation and be able to withstand hightemperature (423 K) and high-pressure (10 bar) tests.

A citric acid-assisted sol-gel method was applied to synthesize green calcium oxide (CaO) sorbents from diverse natural waste (eggshells, crab shells, and green mussel shells for effective CO2 capture). Among them, CaO-gms derived from green mussel shells displayed the most advantageous porous morphological structure with a corallike finger structure and the largest BET surface area and pore volume for textural properties. These properties play a crucial role in the diffusion of CO2 through the pores and surface layer to enhance the interaction of CO2 and interior CaO particles, promoting the highest CO2 capture capacity. CaO-gms demonstrates a remarkable CO2 uptake of 0.69 g -CO2/g-sorbent (or 0.75 g -CO2/g -CaO) at 700 degrees C, with 15 vol% inlet CO2 concentration and a total gas flow rate of 100 mL/min. The sorbent was investigated for its sintering resistance, as it has been a major issue for large-scale deployment of cyclic CO2 capture technology. CaO-gms exhibited robust cyclic performance in carbonation/calcination reactions with no sign of crystallite agglomeration (XRD analysis), maintaining a CO2 uptake of approximately 0.65 g -CO2/g -sorbent (or 0.71 g -CO2/g -CaO) after 20 cycles. The results highlight the excellent resistance of the sorbent to crystallite sintering during the carbonation/calcination reaction sequence.

This study presents a mesoporous material-based catalyst for the CO2 hydrogenation to methanol reaction, utilizing copper nanoclusters (Cu6) immobilized on Zn-modified SBA-15. The Cu6-ZnO-SBA-15 catalysts are prepared by the wet impregnation of ZnO-SBA-15 with various metal loading contents. Multi-technique characterization shows uniform active phase dispersion within or on the mesoporous SBA-15 channels. The catalytic experiments reveal that the catalyst with the lowest copper content (2 wt%) exhibits superior activity with a methanol space-time yield of 232.5 (molMeOH kgCu-1 h-1) and a selectivity of 86%. Furthermore, the confinement of the active phase into the structure of SBA-15 prevents sintering to some extent, implying the excellent stabilization effect of the support. This study highlights the potential of using small nanoclusters prepared by wet chemistry in high-pressure CO2 hydrogenation to methanol.

Ionic liquids construct zeolites with their unique properties, serving as solvents, structure-directing agents, porogens, and post-synthetic modifiers. This approach is reshaping zeolite synthesis and enabling the creation of new frameworks. Graphical abstract image generated with AI.

The utilization of oxygen carrier (OC) with redox durability is crucial for scaling up biomass chemical looping gasification (BCLG) systems. In the present work, two novel OCs were synthesized by chemically and physically incorporating two cements with hematite and tested in a TGA and batch fluidized-bed reactor for BCLG. These OCs exhibited multi-stage release of oxygen at an internally controlled rate, leading to the dominant char partial oxidation followed by combustion of remnant char. This redox behavior significantly enhanced selective syngas production and reduced carbon deposition with or without steam. The characterization results from XRD, XPS, H2-TPR and SEM/EDS techniques reveal that active solid solution containing Fe and inert species (Al and Ca) was retained in the particle interior as Fe dispersity was improved over cycling, thereby preserving sufficient oxygen vacancies. This chemical durability conferred high oxygen anion conductivity on recycled OCs, contributing to the stable solid-solid reaction between OC and char. As a result, the reactivity loss caused by Fe segregation was mitigated. The constant presence of inert phases provided physical framework for active phases within reduction-oxidation cycles. Non-isothermal TGA tests for the solid-solid reaction show that the corresponding activation energy decreased from 801.37 kJ & sdot;mol- 1 (fresh OC) to 542.04 kJ & sdot;mol- 1 (used OC), indicating smoother oxygen mobility after cycling. This study proves that the dissolution of hematite into inert phases such as Ca-Al oxides is a promising approach for OC structure modification to achieve enhanced selectivity and reactivity for syngas production.

This study explores the ionothermal synthesis of MFI-type zeolites using the ionic liquid (IL) [BMIM]Br, with a focus on framework development and functional performance. By tuning synthesis parameters of temperature, Si/Al ratio, and employing a two-step heating strategy, well-crystallized ZSM-5 materials with enhanced porosity were obtained. Structural characterization by XRD, SEM, and N2 physisorption confirmed that the two-step synthesis improved crystallinity and microporosity, while also promoting uniform mesopore formation and better pore accessibility. Functional assessments, including room-temperature N2 adsorption, methylene blue adsorption, and catalytic toluene methylation, were conducted. Using the two-step heating treatment, the N2 adsorption capacity of ionothermally synthesized zeolites increased from 2.57 cm3 g-1 to 3.86 cm3 g-1, and methylene blue adsorption (within 6 h) improved from 61.18 mg/kg to 74.54 mg/kg. Furthermore, toluene conversion rose by 11 %, and xylene selectivity increased by 10 %, confirming the enhanced structural properties achieved through the 2-step heating treatment. Kinetic modeling indicated a shift from diffusion-limited physisorption in single-step samples to chemisorption-driven processes in two-step products. The recyclability of [BMIM]Br was demonstrated after single-step use, but structural degradation occurred following reuse from high-temperature treatments. Comparisons with TPAOH-templated hydrothermal syntheses further highlighted the superior structural direction offered by ILs. These findings advance the understanding of crystal growth in ionothermal systems and emphasize the potential of ILs in tailoring high-performance zeolite materials for catalytic and adsorption applications.

In this study, a novel Fe-based OC was synthesized based on cement chemically bonded hematite, containing multiple-component calcium ferrites. Its cyclic performance was evaluated over 10 cycles of BCLG at 850, 900 and 950 degrees C, respectively, in a batch fluidized-bed reactor. Fresh and used OCs were characterized using TGA, XPS, XRD and SEM/EDS techniques. The best cyclic reactivity was achieved at 950 degrees C, resulting in an average gasification efficiency of 91.3 % and H2/CO ratio of 2.4 due to superior oxygen diffusivity. At 850 degrees C, the OC underwent elemental reorganization under repeated limited reduction and complete reoxidation. This structure evolution significantly improved the high-temperature redox reactivity of the used OC (OC850-M10) with the maximum mass loss rate of-4%/min during the TGA tests, compared to-2.6 %/min for fresh OC. For used OCs after 10 cycles at 900 degrees C (OC900-M10) and 950 degrees C (OC950-M10), increased oxygen vacancies in OC900-M10 compensated for reactivity loss caused by Fe enrichment, while reactive oxygen accessibility in OC950-M10 was moderately constrained by Fe segregation beyond a critical threshold. Despite the agglomeration after 20 cycles at 950 degrees C, enhanced overlaying of Fe and inert species further homogenized Fe phases, allowing for the restoration of 98 % of active oxygen after gentle crushing. Moreover, the addition of cement also improved crushing strength (>3 N) over cycling, partially due to the growth of Al2O3 flower-shaped phases in internal voids. These findings suggest that chemical incorporation of cement with hematite prolonged OC longevity.

This review offers an overview of the pivotal role of oxygen vacancies in advanced oxidation technologies used to remove organic pollutants from water, including photocatalytic, electrocatalytic and photoelectrocatalytic oxidation processes. The fabrication of oxygen vacancies in various catalytic materials as well as the benefits and challenges of oxygen vacancy engineering are addressed in detail. This review provides collective views from various published research reports. The underlying principles and rationale for the roles of oxygen vacancies in the treatment of organic water pollutants are critically assessed, which is the key to designing efficient catalysts and catalytic systems for water purification.

Recent statistics portray a stark reality, particularly highlighting the inadequate recycling measures and the consequent environmental threats, most notably in developing nations. The global ramifications of plastic pollution are elucidated, specifically focusing on the alarming accumulation in regions such as the “Great Pacific Garbage Patch” and evolving waste management practices in Southeast Asian countries. We emphasize the significance of Waste-to-Energy (W2E) and Waste-to-Fuel (W2F) technologies, e.g., pyrolysis and gasification, for converting difficult-to-recycle plastic waste into a dense-energy source. However, we identify a critical gap in current research: the emission of CO 2 during these processes. This perspective spotlights emergent CO 2 capture and utilization technologies, underscoring their role as a robust turnkey solution in making W2E and W2F methods more sustainable and unleashing the huge potential of using waste plastics as a dense-energy source. The scientific community is urged to develop tailored solutions for reducing CO 2 emissions in plastic waste conversion processes. This approach promotes circular resource utilization and realizes the socio-economic and environmental advantages of plastic waste utilization technologies, advocating their implementation in economically disadvantaged regions.

Anthropogenic CO2 emissions have drawn significant attention in recent years. Using CO2 as feedstock for chemical processes has become a key solution in overall closed carbon cycles for a vision of a circular carbon economy. CO2 hydrogenation to higher alcohols has emerged as one of the most promising CO2 conversion pathways for mitigating CO2 emissions and producing value-added chemicals. The present review critically discusses the most recent cutting-edge catalyst development in higher alcohol synthesis (HAS), focusing on the influence of different metals, promoters, and supports according to the contributions of different active species in modern catalyst configurations. Particularly, the critical roles of oxygen vacancies and the reaction mechanisms shed light on the rational design of the next-generation CO2 hydrogenation catalysts.

Ionic liquids (ILs), known for their low melting points and vast array of possible combinations of cations and anions, serve as an ideal template for zeolite synthesis. MFI zeolite, with the distinct three-dimensional porous network, has attracted wide interest in petrochemical processes and environmental applications. In this study, we used 1-butyl-3-methylimidazolium (BMIM)-based ILs for MFI-type zeolite synthesis, successfully achieving a highly crystallized MFI-type crystal within 18 h. To highlight the benefits of using ILs, ZSM-5 zeolite synthesized using the conventional template, tetrapropylammonium hydroxide, was prepared for comparative analysis. Parameters including ion variations, aging duration, and aluminate content on crystal phase growth were explored. Furthermore, seed-assisted synthesis was carried out to verify the impact of the IL on the nucleation step. The mechanism underlying the accelerated crystallization process was subsequently elucidated, revealing that the inclusion of BMIM in the synthesis gel significantly contributed to rapid nucleation. This was followed by the immediate formation of amorphous particles. These particles then experienced inward growth, culminating in the development of well-crystallized particles. This discovery underscores the promising potential of ILs for efficient zeolite synthesis.

Oxygen carriers (OCs) are the key to developing biomass chemical looping gasification (BCLG), a promising technique for producing syngas from renewable resources. The tested OC pellets mainly contain SFCA-type oxides - khesinite (Ca5Al2Fe173+Mg1.5Si2.5O40) and Ca-Al-Fe-O (Ca5.1Al9.3Fe18.73+Fe0.92+O48) - with a polyhedron-enriched structure containing high oxygen vacancies. Nonisothermal tests coupled with kinetic analysis methods and characterization techniques are conducted to investigate the interaction mechanism between biomass-derived intermediates and SFCA-type OCs during BCLG. The results show that the SFCA-type OCs significantly promote char conversion with a high reaction rate. OCs exhibit a unique reduction pathway during the solid-solid reaction between OCs and char. This redox reaction is controlled by the nucleation mechanism for conversion (alpha) below 0.65, which shifts to the coupled nucleation and diffusion mechanism for higher conversion (alpha >= 0.65). These results are useful for evaluating the possible application of SFCA-type OCs in the BCLG system and optimizing the complex OC structure.

Various commercial zeolites, including FER, MOR, ZSM‐5, BEA, and FAU frameworks, were treated with NH 4 F aqueous solutions to study the effects of fluoride etching on different zeolite frameworks. NH 4 F‐treated small‐medium pore FER, MOR, and ZSM‐5 samples showed much higher mesoporosities than the untreated ones without alteration of the structural compositions and acidic properties. On the other hand, the 12‐membered ring zeolites BEA and FAU showed severe dissolution of the framework aluminosilicate structure after NH 4 F etching due to the high accessibility of fluoride species into the framework structures. The effect of NH 4 F concentration on the fluoride treatment of H‐ZSM‐5 zeolite was specifically studied. From the results, we observed that structural etching with 20 wt % NH 4 F was optimal for fabricating open‐pore H‐ZSM‐5 zeolite and resulted in a high mesoporosity with comparable relative crystallinity and acidity with respect to the untreated H‐ZSM‐5. The catalytic activities of the open‐pore H‐ZSM‐5 were evaluated with acid‐catalyzed methanol and bioethanol conversions. Remarkably, the hierarchical open‐pore H‐ZSM‐5 zeolite fabricated via fluoride etching exhibited an enhanced catalytic performance in bioethanol conversion with >85 % conversion over 34 h TOS and a higher catalytic stability in methanol conversion than the parent H‐ZSM‐5 (~50 % of bioethanol conversion at 34 h TOS).

The circular economy represents an economic model that prioritizes sustainability and resource efficiency, aiming to minimize waste minimization, promote reuse, and close material loops. This Special Collection highlights recent advancements in green chemistry, catalysis, and waste valorization, fields critical for achieving sustainable practices and resource efficiency within a circular economy. Researchers from the Asia-Pacific region, Europe, South America, and North America have contributed to designing sustainable chemical processes that minimize environmental impact. These efforts involve developing efficient reactions to reduce waste generation and resource depletion. Additionally, this Special Collection showcases examples of effective catalysts with the potential to enhance resource conservation and circularity and convert waste and biomass materials into valuable products.