Gradient Porous Structured MnO2-Nonwoven Composite: A Binder-Free Polymeric Air Filter for Effective Room-Temperature Formaldehyde Removal

Thermocatalytic Degradation of Gaseous Formaldehyde Using Transition Metal-Based Catalysts

Formaldehyde (HCHO: FA) is one of the most abundant but hazardous gaseous pollutants. Transition metal oxide (TMO)-based thermocatalysts have gained much attention in its removal due to their excellent thermal stability and cost-effectiveness. Herein, a comprehensive review is offered to highlight the current progress in TMO-based thermocatalysts (e.g., manganese, cerium, cobalt, and their composites) in association with the strategies established for catalytic removal of FA. Efforts are hence made to describe the interactive role of key factors (e.g., exposed crystal facets, alkali metal/nitrogen modification, type of precursors, and alkali/acid treatment) governing the catalytic activity of TMO-based thermocatalysts against FA. Their performance has been evaluated further between two distinctive operation conditions (i.e., low versus high temperature) based on computational metrics such as reaction rate. Accordingly, the superiority of TMO-based composite catalysts over mono- and bi-metallic TMO catalysts is evident to reflect the abundant surface oxygen vacancies and enhanced FA adsorptivity of the former group. Finally, the present challenges and future prospects for TMO-based catalysts are discussed with respect to the catalytic oxidation of FA. This review is expected to offer valuable information to design and build high performance catalysts for the efficient degradation of volatile organic compounds.

Overexpression of CcFALDH from spider plant (Chlorophytum comosum) enhances the formaldehyde removing capacity of transgenic gloxinia (Sinningia speciosa)1

Formaldehyde can cause leukemia and nasopharyngeal cancer in humans, and is a major indoor air pollutant. In this study, to improve the ability of flowering plants to purify formaldehyde, we cloned the CcFALDH gene encoding formaldehyde dehydrogenase (FALDH) from the spider plant (Chlorophytum comosum), which encodes 379 amino acids with the alcohol dehydrogenase (ADH) structural domain, and used it to transform the flowering plant gloxinia (Sinningia speciosa). The FALDH activity of transgenic gloxinia was 1.8-2.7 times that of wild-type (WT) with a considerable increase in formaldehyde stress tolerance. The activities of the antioxidant enzymes SOD, POD, and CAT of transgenic gloxinia were 1.5-2.0 times those of the WT under formaldehyde stress; H₂O₂, O^2-, and MDA contents were markedly lower than those in WT. Liquid formaldehyde and gaseous formaldehyde were metabolized at 2.1-2.8 and 2.1-2.7 times higher rates in transgenic gloxinia than in WT. Our findings indicate that overexpression of CcFALDH can enhance the capacity of flowering plants to metabolize formaldehyde, which provides a new strategy to tackle the indoor formaldehyde pollution problem.

Advanced Dual-Function Hollow Copper-Sulfide-Based Polyimide Composite Window Film Combining Near-Infrared Thermal Shielding and Organic Pollutants' Photodegradation

Window-film-integrated, near-infrared (NIR) absorption-based nanomaterials are of great interest in terms of numerous demands to reduce energy consumption, especially in buildings and vehicles. However, the question of how to effectively manage thermal energy generated from NIR harvesting in light-absorbing materials, rather than being wasted or causing negative effects, remains challenging. Herein, hollow copper sulfide (Cu2-xS) on colorless polyimide (PI) films, enabling them to be well-dispersed and robustly adhered, underwent in situ growth fabrication and were utilized as NIR-thermal-shielding and organic-pollutant-removal dual-function window films. Due to strong NIR absorbance, arising from the heavy hole-doping (copper cation deficiency), the Cu2-xS/PI composite film exhibited great promise for use in the filtration of the NIR spectrum. By monitoring Cu2-xS densities, its NIR-shielding efficiency reached 69.4%, with hundred-percent UV blocking and consistent performance within the reliability (85 °C/85%RH) tests over one week as well as 5000 bending cycles. The integration of the films into model cars and building windows exhibited excellent thermal-shielding performance upon exposure to direct sunlight. Moreover, benefiting from the distinctive distribution of Cu2-xS, the additional thermal energy (holes) generated in NIR absorption was successfully utilized. The densely surface-confined hollow structure of Cu2-xS on PI significantly endowed good formaldehyde catalytic capacity, with removal efficiency reaching approximately 72% within 60 min and a negligible decline after quartic reuse. These integration methodologies enable the promising fabrication of a high-performance, bifunctional window film combining thermal shielding and indoor organic pollutant removal.