Formaldehyde (FA), a carcinogenic oxygenated volatile organic compound, represents a principal challenge for indoor air quality management efforts. This study investigates the oxidation potential of lead(ii) oxide (PbO)-supported silver (Ag) catalysts against FA under dark and low-temperature conditions, including room temperature (RT) conditions. FA (100 ppm) conversion (X FA) on Ag/PbO increases with increasing Ag content while being lowered with reduction pre-treatment (R). The RT X FA of these catalysts decreases (at gas hourly space velocity: 9436 h-1) as follows: 0.9%-Ag/PbO (83%) > 0.9%-Ag/PbO-R (56%) > 0.2%-Ag/PbO (39%) > 0.02%-Ag/PbO (35%). Interestingly, the 0.9%-Ag/PbO catalyst achieves 100% X FA at RT above 60% relative humidity, demonstrating exceptional FA removal efficiency. While complete mineralization to carbon dioxide requires a mild temperature increase to 80 °C, the catalyst effectively sequesters FA as surface-bound intermediates (e.g., dioxymethylene and carbonates) at RT, functioning as a transformative adsorptive sink. Density functional theory calculations and characterization results reveal that the Ag/PbO interface effectively activates molecular oxygen (O2) and water (H2O) to generate reactive oxygen species (*O) and hydroxyl (OH) groups for the oxidation of FA molecules. Compared to Ag/PbO-R, the Ag/PbO surface exhibits a higher concentration of *O under oxidative operational conditions, as oxygen species preferentially accumulate at interfacial sites rather than being consumed to restore the lattice structure. Additionally, moisture plays a crucial role by facilitating the formation of *OH as well as the key *CH2(OH)2 intermediate. This study mechanistically dissects the charge-transfer dynamics at the Ag-PbO interface and the cooperative O2/H2O chemistry that arises from this junction.

Joule heating-driven catalysis represents a transformative approach for the energy-efficient abatement of volatile organic compounds (VOCs). This review provides a critical analysis of this burgeoning field, where an electrically conductive monolith functions as a catalyst support and an in-situ resistive heater. This strategy enables a paradigm shift from inefficient, bulky external heating to rapid, on-demand thermal control within compact reactors, demonstrating energy savings exceeding 85% and response times an order of magnitude faster than conventional methods. This work systematically examines the catalyst systems developed on carbon-based, metal alloy, and metal foam substrates, revealing three-dimensional architectures like carbon monoliths and nickel foams vastly outperform simpler geometries. A quantitative performance comparison identifies state-of-the-art systems capable of achieving >90% VOC conversion using just a few Watts of power. Delving into mechanistic insights, this review elucidates how the applied electric field acts as a non-thermal promoter. It enhances surface acidity, modulates the redox state of active metals, and increases the mobility of lattice oxygen, thereby accelerating the Mars-van Krevelen reaction pathway at significantly lower temperatures. Furthermore, it explores the frontier of electro-assisted photothermal systems, where photonic and electronic inputs create powerful synergistic effects. The review concludes by identifying research gaps and future directions.

Formaldehyde (FA) is a pervasive and harmful indoor air pollutant that poses significant health risks. While photocatalytic oxidation is a promising technology for its abatement, conventional photocatalysts, including pristine metal-organic frameworks (MOFs), suffer from limitations such as rapid electron-hole recombination and a narrow light absorption range. This review systematically summarizes and critically analyzes the recent progress in modifying MOF-based materials to enhance their photocatalytic efficiency for gaseous FA degradation. The primary modification strategies are detailed, including the construction of MOF/semiconductor heterojunctions (e.g., Z-scheme and step (S)-scheme), plasmonic enhancement via the incorporation of noble metal nanoparticles, defect engineering to create unsaturated metal sites and bimetallic active centers, and the integration of polar or carbonaceous materials to build internal electric fields and facilitate charge transport. Mechanistic insights are discussed, highlighting the crucial synergistic role of the MOF adsorption capability to capture and concentrate reactants, along with charge separation pathways that lead to the generation of reactive oxygen species. Furthermore, the successful translation of these advanced powdered materials into practical application formats such as functional coatings and flow-through air filters is examined, with a focus on their performance, stability, and durability. Finally, this review outlines the persistent challenges related to cost, scalability, and standardization, and provides a forward-looking perspective on the future research directions needed to bridge the gap between laboratory breakthroughs and real-world application.

Palladium-loaded activated carbon (Pd/AC) catalysts with ultralow metal loadings (0.05–0.5 wt.%) are developed to leverage the synergistic potential of microporous supports for low-temperature VOC oxidation. The optimized 0.5 wt.% Pd/AC catalyst demonstrates exceptional performance, achieving 90% conversion (T₉₀) of 10 ppm toluene at 200 °C under a high gas hourly space velocity (52,105 h⁻¹). In contrast, formaldehyde (FA) requires a higher temperature of 275 °C (at 100 ppm) to reach T₉₀ under comparable conditions. Conversion of both VOCs exceeds 90%, while the CO2 yield reaches up to 18.7%. Mechanistic insights from in-situ DRIFTS and DFT simulations reveal divergent oxidation pathways. The oxidation of FA proceeds via dioxymethylene and formate intermediates. In contrast, toluene oxidation initiates with aromatic ring activation, followed by C–H and C–C bond cleavage to form phenolic and carboxylate species. The superior catalytic activity of Pd/AC is attributed to the high dispersion of Pd species and enhanced redox properties, which together facilitate efficient oxygen transfer. These findings underscore the robust potential of low-loading Pd/AC for energy-efficient VOC abatement, particularly for recalcitrant aromatic compounds.

Methyl ethyl ketone (MEK) is a prevalent oxygenated volatile organic compound (VOC) whose complex oxidation behavior makes it an important model molecule for catalysis studies. Its abatement is complicated by competing C-C bond scission versus dehydrogenation pathways, the prevalence of which is highly dependent on catalyst design. This is the first comprehensive review dedicated specifically to MEK thermocatalytic abatement, focusing on catalyst development, reaction mechanisms, and performance metrics. Its single-molecule focus enables a deeper mechanistic analysis than is possible in broader VOC surveys, clarifying structure-performance relationships. We critically examine supported noble metal catalysts (SNMCs) and transition metal oxides (TMOs), covering the roles of supports, promoters (e.g., manganese oxide (MnOx) and cerium dioxide (CeO2)), and nanostructure. While SNMCs offer high activity at low temperatures, TMOs like perovskites and MnOx emerge as cost-efficient alternatives. The review contrasts how catalyst properties dictate pathway selectivity. Practical challenges from co-contaminants (e.g., water, sulfur, and chlorine) and strategies to enhance stability are discussed. A comparative performance analysis underscores that catalyst selection depends on the desired optimization metric. The review concludes by identifying critical research gaps, emphasizing the need for standardized protocols and long-term stability studies to bridge laboratory and industrial applications.

The photocatalysts, silver (Ag)-incorporated manganese dioxide (MnO2) composites (AM-x), are designed as Schottky junction materials to promote the photomineralization of gaseous H2S. Under low-intensity ultraviolet light (0.98 W), the best performing AM-7 achieves 100% removal of H2S in 330 s with an apparent quantum yield of 0.74%. The photocatalyst also shows excellent stability, maintaining this performance even after six cycles. Its clean air delivery rate (14.14 L min- 1) exceeds that of TiO2 and MnO2 by 55.6 and 25.2 times, respectively. Insitu spectroscopy and elemental analysis demonstrate that H2S photodegradation proceeds via the formation of sulfate (SO42- ) species, a pathway greatly accelerated under humid conditions. Optical characterization confirms the superiority of AM-7 through the formation of a Schottky junction and enhanced light absorption/utilization. DFT calculations and in-situ XPS reveal that an interfacial electric field at the Schottky junction facilitates charge separation by transferring photo-generated electrons from the Fermi level (occupied states) of Ag to the conduction band (unoccupied states) of MnO2 nanoparticles, effectively suppressing electron-hole recombination. This study provides insight into the rational design of highly efficient Schottky junction photocatalysts, highlighting their enhanced charge separation and potential for effective environmental remediation under ambient conditions.

The photocatalytic removal of volatile organic compounds from indoor air continues to be constrained by two key limitations of conventional titanium dioxide (TiO2) catalysts: insufficient adsorption capacity and rapid charge carrier recombination. To overcome these dual constraints, an interface engineering strategy is employed by integrating TiO2 with microporous activated carbon functionalized via mineral-acid treatment. The resulting acid-treated carbons are denoted as AC-X, where X indicates the acid type: N (nitric, HNO3), C (hydrochloric, HCl), S (sulfuric, H2SO4), and P (phosphoric, H3PO4). The acid-induced oxygenated surface groups on AC-X simultaneously enhance toluene adsorption and facilitate interfacial charge transfer in the resulting TiO2-ACX composites, designated as TA-N, TA-C, TA-S, and TA-P, respectively. Among these, TA-N shows the highest toluene removal efficiency (98.7%), carbon dioxide yield (93.8%), and a dynamic clean air delivery rate of 9.87 L mg-1 min-1. It further exhibits robust performance across a range of relative humidity (0-80%), toluene concentrations (1-10 ppm), and flow rates (100-300 mL min-1) with an apparent quantum yield of 0.03%. Mechanistic analysis confirms the critical role of oxygenated surface groups in promoting pollutant adsorption and accelerating oxidative mineralization, demonstrating the potential of acid-functionalized TA composites as a robust next-generation platform for indoor air purification.

The design of a photocatalyst is crucial for the efficient photocatalytic oxidation (PCO) of indoor air pollutants like volatile organic compounds (VOCs). A highly effective strategy for enhancing photocatalytic activity is the construction of step (S)-scheme heterojunctions, which are engineered by coupling semiconductors such as n-type zinc hydroxystannate (ZnSn(OH)6, ZS) with n-type titanium dioxide (TiO2, T). The potential of the formed ZST photocatalyst is explored for the PCO of 1 ppm benzene under 1 W ultraviolet (UV) irradiation. It achieves a clean air delivery rate of 1.71 L min-1 with a 10 % removal efficiency rate of 21.9 µmol g-1 h-1 and a mass-normalized apparent quantum yield of 6.08 × 10-4 molecule photon-1 g-1. The PCO activity of ZST is further assessed under several process variables. In situ DRIFTS analysis indicates that benzene mineralization proceeds through phenolate, acetate, maleate, and methylene reaction intermediates. Theoretical analyses (charge density difference and electron localization function) confirm an interfacial S-scheme electron transfer from ZnSn(OH)6 to TiO2. This mechanism effectively separates highly reactive carriers while promoting recombination of less active species. As such, ZST photocatalyst achieves efficient mineralization of gaseous benzene into carbon dioxide (CO2) and water (H2O). These findings provide valuable insights for designing high-performance catalytic systems against robust aromatic hydrocarbons like benzene.

Objective. More than 130 susceptibility loci for rheumatoid arthritis (RA) have been identified with genomewide association studies. To investigate the genetic predisposition of Chinese patients to anticitrullinated protein antibody (ACPA)-positive RA, we carried out an exome sequencing study. Methods. Patients were recruited from 3 major public hospitals in Singapore: Tan Tock Seng Hospital (TTSH), Singapore General Hospital, and the National University Hospital. Controls came from an established exome collection and from the TTSH Health Control Biobank. All the participants were of Chinese descent. We performed whole-exome sequencing (WES) in 595 ACPA-positive patients with RA and 1281 controls and validated the candidate variants by genotyping 795 RA cases and 600 controls. Results. The discovery cohort yielded 73 susceptibility single-nucleotide variants (SNVs) that reached statistical significance. In the validation study with an independent cohort, 2 SNVs remained significant: PCNXL4 (P = 1.50 x 10-5) and DHRS7 (P = 6.02 x 10-5). The majority of known susceptibility foci were not captured by exome sequencing. Conclusion. In this WES study of ACPA-positive RA in Chinese patients, we discovered 2 new variants in PCNXL4 and DHRS7 associated with risk for RA.

scRNA-seq of gastric tumor and normal samples defines 34 cell states including rare cell populations. A, Schematic representation of experimental design and techniques used in this study. Thirty-one unique patients with gastric cancer undergoing surgical resection or endoscopy had tumor samples (n = 31) and adjacent normal samples (n = 11) harvested for analysis. Tumors ranged from stage I to IV and included samples of both primary tumors, distant (peritoneal) metastases, and matched normal gastric tissues. Twenty-nine tumors had scRNA-seq performed using the 10× platform (along with 11 adjacent normal tissues). Four patients had PDOs generated from their tumors (4 tumors + 4 adjacent normal), which were also sequenced by 10× scRNA-seq. A subset of 13 samples also had DSP performed using the NanoString GeoMx platform (10 tumor + 3 normal). In total, more than 200,000 cells were sequenced in this study. B, Uniform Manifold Approximation and Projection (UMAP) of 152,423 cells representing 34 unique cell states color-coded by their corresponding cell lineage or subtype. Each dot in the UMAP represents a single cell. C, Cell-lineage compositions of gastric cancer and normal samples inferred by scRNA-seq data. Middle (bubble plot), cell subclusters (rows) by tumor versus normal, stage, and gastric cancer histologic subtype (diffuse vs. intestinal). The size of the circle represents the cell proportion of each specific cell lineage/type. The circles are color-coded by defined cell lineages/types as shown in B. The stacked bar graph on the top shows the number of cells in each meta-cluster for each category. The histogram on the right shows the absolute cell numbers in each subcluster. D, Cluster–cluster heat map of gene-expression data of all 34 cell states across all samples using Pearson correlation matrix. Darker colors correspond to higher correlation. E, Pseudotime analysis of plasma metacluster generated using Monocle. The trajectory was rooted against the plasmablasts. Pseudotime analysis demonstrates different stages of plasma cell differentiation and maturation including plasmablasts, short-lived plasma cells, and long-lived plasma cells. F, Expression of PLVAP and RGS5 in endothelial (STE2) and fibroblast (STF2 and STF4) clusters. Doublets were identified and filtered out using DoubletFinder. PLVAP+RGS5− cells are predominantly present in the endothelial cluster (STE2). PLVAP−RGS5+ cells are predominant in the fibroblast cluster (STF2). The STF4 cluster shows cells expressing PLVAP+RGS5+, suggestive of a rare mixed-lineage population.

Efficient removal of formaldehyde (FA) under practical conditions remains challenging because of limitations in common remediation tools, such as low FA adsorption capacity and/or poor charge separation efficiency under weak illumination (visible or ultraviolet (UV)). To overcome these challenges, a redox-active organic-inorganic hybrid system has been developed by modifying titanium dioxide (TiO2) with diaminopropane (DAP). The resulting DAP/TiO2 composite is integrated into a prototype air purifier (AP) and operated under low UV light intensity (25.9 ​W ​m−2) at a flow rate of 160 ​L ​min−1. Mechanistic studies reveal that the amine (-NH2) groups in DAP enhance FA adsorption and facilitate electron accumulation at the lowest unoccupied molecular orbital (LUMO), promoting superoxide radical formation. Concurrently, DAP induces oxygen vacancies and surface band bending on TiO2, improving charge separation and generating highly oxidizing holes. The optimal 1%-DAP/TiO2 delivers performance metrics far surpassing those of pure TiO2, including a clean air delivery rate of 23.3 ​L ​min−1, a kinetic rate of 0.84 ​mmol ​h−1 ​g−1 at a 10% removal efficiency (RE), and a mass-normalized apparent quantum yield of 0.106 molecules photon−1 g−1. This superior activity is supported by density functional theory simulation, which reveals that DAP adsorption on oxygen-deficient TiO2 surfaces successfully induces band-edge shifts and surface hydroxylation to enhance photocatalytic mechanism. Ultimately, these findings provide a rational design strategy for hybrid photocatalysts and mechanistic insights necessary for practical FA abatement in indoor air purification.

The development of photocatalytic degradation (PCD) system is one of the most effective options for the remediation of aromatic volatile organic compounds (VOCs) in indoor air. To achieve this, a titanium dioxide (TiO2)-based photocatalyst has been engineered through co-modification with sodium (Na) and palladium (Pd). Its efficacy in the PCD reaction is achieved through a Schottky junction formed between Pd nanoparticles (NPs) and Na-doped TiO2. The PCD efficiency (XT) of this Pd/Na-TiO2 against toluene (4 ppm at 20 % relative humidity (RH) and a gas hourly space velocity of 3 h- 1) is 75.3 % (CO2 yield of 44.5 %). This represents 1.2- and 1.4-fold increases compared to Pd/TiO2 and TiO2, respectively. Pd/Na-TiO2 achieves the highest dynamic clean air delivery rate (D-CADR) of 40.2 L h- 1 g- 1. Its PCD performance, evaluated in terms of apparent quantum yield (AQY), reaches 0.113 %, which is significantly higher than that of TiO2 (0.084 %) and Pd/TiO2 (0.097 %). The Schottky junction with oxygen vacancies (OVs) facilitates the transfer of photogenerated electrons to the Pd NPs, enhances the separation efficiency of electron-hole pairs, and promotes the generation of reactive oxygen species (i.e., superoxide anion and hydroxyl radicals). Density functional theory calculations reveal that Na promotes molecular oxygen (O2)/water (H2O) activation, Pd acts as the toluene adsorption site, and OVs donate electrons to facilitate photocatalytic degradation under humid conditions. This study addresses the challenge of eliminating persistent aromatic air pollutants by engineering a photocatalytic system where tuned surface defects (OVs) and sodium-promoted palladium sites work in concert. The integration of these synergistic interactions is demonstrated to be the key to unlocking high-efficiency VOC destruction, paving the way for advanced air purification technologies.

In the present research, titanium dioxide (TiO2) is paired with silicon carbide (SiC) as TiO2-SiC-x (x (wt.% of SiC over TiO2) = 1, 5, and 10). The prepared photocatalysts are anchored on the filter unit of a portable air purifier and used for removing formaldehyde (FA) from indoor air under ultraviolet (UV) irradiation (0.98 W). TiO2-SiC5 is superior to the others when tested against 1 ppm FA (0 % relative humidity at 160 L min- 1) with kinetic removal rate of 2.09E + 02 mu mol g- 1 h- 1 (at 100 % removal efficiency (XFA)), space-time yield (STY: 1.91E-05 molecules photon- 1 mg- 1), and clean air delivery rate (CADR: 18.53 L min- 1)). Furthermore, TiO2-SiC-5 maintains stable performance (e.g., XFA = 100 % and CADR = 18.50 L min- 1 over five reuse cycles) to reflect the unique properties of n-n type step (S)-scheme photocatalysts in the separation and migration of photogenerated charge carriers, as evidenced through various routes (e.g., electrochemical impedance spectroscopy, UV-visible diffuse reflectance spectroscopy, and transient photocurrent response). The FA molecules are mineralized into carbon dioxide and water through multiple reaction intermediates (e.g., dioxymethylene and formate). Density functional theory simulations indicate that both the silicon and carbon centers are involved in activating molecular oxygen while FA oxidation reaction occurs primarily near the carbon sites on the TiO2-SiC surface. The overall findings provide better insights into the efficacy of TiO2-SiC as S-scheme photocatalysts for practical use in environmental remediation.

In the present study, the oxidative removal of benzene (model carcinogenic aromatic volatile organic compound (VOC)) from indoor air is investigated using titanium carbide (Ti3C2) MXene/anatase titanium dioxide (TiO2)-supported gold (Au) catalysts under dark and low-temperature (DLT: 30-90 °C) conditions. The reduction pre-treatment (catalyst labelled with the 'R' suffix) has been used to form metallic Au (Au0) nanoparticles and anatase TiO2 in the MXene structure. The relative ordering in the Au catalysts, if assessed in terms of room-temperature (RT) benzene (5 ppm) conversion (XB (%)) at 10,191 h-1 gas hourly space velocity, is found as: 0.5 %-Au/Ti3C2-R (85 ± 5.5 %) > 0.2 %-Au/Ti3C2-R (71 ± 1.8 %) ≈ 0.5 %-Au/Ti3C2 (71 ± 2.8 %) > 1 %-Au/Ti3C2-R (52 ± 5.8 %). The catalytic activity peaks at 0.5 wt% Au loading with reduction pre-treatment and is further enhanced by decreasing the flow rate, benzene concentration, and relative humidity (or by increasing the catalyst mass). The 0.5 %-Au/Ti3C2-R catalyst maintains stable benzene mineralization for 24 h time-on-stream (maximum tested reaction time) at RT without noticeable deactivation. Benzene oxidation on the 0.5 %-Au/Ti3C2-R surface proceeds through diverse reaction intermediates (e.g., phenolate, catecholate, o-, p-benzoquinone, formate, and carbonate). The adsorption of benzene and molecular oxygen (O2) occurs near the Au0 sites. Hydrogen first migrates from benzene to O2, forming an -OOH group attached to Au0. Subsequently, hydrogen transfers from benzene to -OOH, leading to the formation of water as the final product. The benzene ring is then unzipped to yield carbon dioxide through various reaction steps. The present work offers insights into developing Au catalysts for practical DLT control of indoor air pollutants.

Formaldehyde (FA) is a carcinogenic oxygenated volatile organic compound and a key constituent of indoor air pollution. Photocatalytic oxidation (PCO) is a promising strategy for managing FA in indoor environments. Here, the PCO of FA in indoor air has been investigated by modifying TiO 2 with KOH (KOH/TiO 2 : expressed as KT‐x, where x = the molar concentration of KOH from 0.1–2 m ). The KOH treatment achieves superior FA removal performance of KT‐0.1 over TiO 2 (e.g., space‐time yield: 1.78E−03 versus 9.91E−04 molecules photon −1 mg −1 and dynamic clean air delivery rate: 10 versus 5.43 L mg −1 min −1 ). Such differences in photocatalytic activity reflect an enhancement in charge separation, molecular oxygen activation (on the photocatalyst surface), and electron mobility facilitated by the presence of surface hydroxyl groups and potassium on the TiO 2 surface. On the KT‐x surface, the PCO of FA proceeds through several reactive intermediates (e.g., formate and dioxymethylene). According to density functional theory, the PCO of FA by KT‐x is promoted by the synergistic combination of oxygen vacancies and potassium impurities on the TiO 2 surface. This research offers valuable insights into the development of cost‐effective photocatalysts with enhanced PCO performance.

Cost-effective thermocatalysts are essential for broadening the application of catalytic systems in environmental remediation. The broad application of many transition-metal oxides, nonetheless, remains constrained by their inherent limitations in catalytic activity or durability. In response, copper cobaltite (CuCo2O4 (CCO)) is synthesized as a bifunctional mixed metal-oxide catalyst using various solvents: deionized water (DI), ethanol (ET), ethylene glycol (EG), and glycerol (GL). These CCO catalysts are then employed for the catalytic oxidation of gas-phase formaldehyde (FA) in air. In terms of reaction kinetics, the performances of catalysts are measured by the temperature (T-90) required to achieve 90 % conversion of FA (100 ppm), using a 30 mg catalyst at a space velocity of 100,000 mL g(-1)h(-1) under 0 % relative humidity. The T-90 values followed this order: CCO-DI (90 degrees C) < CCO-GL (114 degrees C) < CCO-ET (118 degrees C) < CCO-EG (148 degrees C). The enhanced performance of the optimized catalyst, CCO-DI, is attributed to a combination of its high reducibility, abundant oxygen vacancies, high surface area, and oxygen mobility/activation. The catalytic activity of CCO-DI has also been evaluated across various process variables. Its improved activity, even in the presence of low moisture, suggests facile oxygen adsorption and transfer, likely mediated by hydroxyl groups from the H2O dissociation. Furthermore, density functional theory simulations indicate that the catalytic oxidation of FA proceeds via the Mars-van Krevelen mechanism, while dioxymethylene and formate are identified as the key intermediates in the FA oxidation reaction. This work provides an effective strategy for catalyst design by demonstrating the effectiveness of solvent engineering in enhancing FA oxidation performance.