Metal organic framework derived NaCoxOy for room temperature hydrogen sulfide removal

Lignin-derived carbon quantum dot/PVA films for totally blocking UV and high-energy blue light

Excessive exposure to UV and high-energy blue light (HEBL) can cause fatal eye and skin injuries. As a result, it is crucial to protect our bodies from UV and HEBL radiation. To achieve complete blocking of UV and HEBL, we developed a lignin-derived carbon quantum dot (L-CQD)/polyvinyl alcohol (PVA) film. L-CQD was synthesized from lignin, a waste woody biomass, and then blended with a PVA matrix to create a flexible L-CQD/PVA film. Thanks to simultaneous UV and HEBL absorption characteristics and bright color of L-CQD, the PVA film with 0.375 wt% L-CQD demonstrated outstanding blocking efficiency: 100 % in UV-C, UV-B, and UV-A, and at least 99.9 % in HEBL. It also exhibited a 44 % increase in lightness and a 12 % enhancement in transparency compared to lignin/PVA film. The film's ability to block UV and HEBL was further demonstrated by reducing >40 % UV-induced ROS formation in both cancerous and normal cell lines (Hs 294T, HeLa, CCD-986sk, and L929), as well as by blocking blue laser diode (LD) and LED. Since the L-CQD/PVA film is simple to produce, environmentally friendly, flexible, and thermally stable, it is suitable for use as a protective coating against sunlight and harmful emissions from IT devices.

Novel application of sodium manganese oxide in removing acidic gases in ambient conditions

In this study, we have demonstrated the application of sodium manganese oxide for the chemisorption of toxic acidic gases at room temperature. The fabricated alkali ceramic has Na_0.4MnO₂, Na₂Mn₃O₇, and Na_xMnO₂ phases with a surface area of 2.6 m² g^-1. Na-Mn oxide was studied for oxidation of H₂S, SO₂, and NO₂ gases in the concentration range of 100-500 ppm. The material exhibited a high uptake capacity of 7.13, 0.75, and 0.53 mmol g^-1 for H₂S, SO₂, and NO₂ in wet conditions, respectively. The material was reusable when regenerated simply by soaking the spent oxide in a NaOH-H₂O₂ solution. While the H₂S chemisorption process was accompanied by sulfide, sulfur, and sulfate formation, the SO₂ chemisorption process yielded only sulfate ions. The NO₂ chemisorption process was accomplished by its conversion to nitrite and nitrate ions. Thus, the present work is one of the first reports on alkali ceramic utilization for room-temperature mineralization of acidic gases.

Fabrication of Na0.4MnO2 Microrods for Room-Temperature Oxidation of Sulfurous Gases

Phase pure Na_0.4MnO₂ microrods crystallized in the orthorhombic symmetry were fabricated for the wet oxidation of H₂S and SO₂ gases at room temperature. The material was found highly effective for the mineralization of low concentrations of acidic gases. The material was fully regenerable after soaking in a basic H₂O₂ solution.

Probing the origin and stability of bivalency in copper based porous coordination network and its application for H2S gas capture

A bivalent Cu(I,II) metal–organic framework (MOF) based on the 4,4′,4″-s-Triazine-2,4,6-triyl-tribenzoate linker was synthesized via a solvothermal method. The MOF possessed 43.8% of the Cu sites as Cu⁺ with a surface area of 1257 m² g⁻¹. The detailed spectroscopic analysis confirmed dimethylformamide (DMF) solvent as the reductant responsible for Cu⁺ sites in the synthesized MOF. The Cu⁺ sites were easily accessible and prone to oxidation in hot water or acidic gas environment. The MOF showed water-induced structural change, which could be partially recovered after soaking in DMF solvent. The synthesized MOF showed a high hydrogen sulfide (H₂S) uptake capacity of 4.3 mmol g^–1 at 298 K and an extremely low H₂S pressure of 0.0005 bar. The adsorption capacity was the highest among Cu-based MOFs with PCN-6-M being regenerable, which made it useful for deep desulfurization applications. The adsorbed H₂S was mineralized to sulfide, sulfur, and sulfates, mediated by the Cu⁺/Cu²⁺ redox cycle in the presence of adsorbed water and molecular oxygen. Thus, the study confirmed that DMF as a reductant is responsible for the origin of bivalency in PCN-6-M and possibly in other Cu-based MOFs reported in the literature. Also, the developed MOF could be a potential candidate for flue gas desulfurization and gas purification applications.

Role of Bimetallic Solutions in the Growth and Functionality of Cu-BTC Metal-Organic Framework

Bimetallic solutions play a vital role in the growth and functionality of copper trimesate (Cu-BTC) metal–organic frameworks (MOFs). The effect of Ag⁺, Ca²⁺, Mn²⁺, Co²⁺, and Zn²⁺ on the growth of Cu-BTC was studied by fabricating M-Cu-BTC MOFs at room temperature using bimetallic M-Cu solutions. While Ag⁺ in the MOF had a rod-like morphology and surface properties, divalent cations deteriorated it. Moreover, unconventional Cu⁺ presence in the MOF formed a new building unit, which was confirmed in all the MOFs. Apart from Ag and Mn, no other MOF showed any presence of secondary cations in the structure. While Ag-Cu-BTC showed an improved H₂S uptake capacity, other M-Cu-BTC MOFs had superior organic pollutant adsorption behavior. Thus, we have demonstrated that the physicochemical properties of Cu-BTC could be modified by growing it in bimetallic solutions.

Metal-organic framework-derived NaMxOy adsorbents for low-temperature SO2 removal

This work reported the fabrication of NaM_xO_y-type adsorbents from air calcination of (Na, M)-trimesate metal-organic frameworks. NaMn_xO_y (NMO) crystallized as disc-shaped microsheets, whereas NaCo_xO_y (NCO) crystallized as smooth microsheets with surface deposition of polyhedral nanoparticles. The oxides have a surface area of 1.90-2.56 m² g^-1. The synthesized adsorbents were studied for low-temperature SO₂ removal in breakthrough studies. The maximum adsorption capacity of 46.8 mg g^-1 was recorded for NMO at 70 °C. The adsorption capacity increased with the increasing temperature due to the chemisorptive nature of the adsorption process. The capacity increased with the increasing bed loading and decreasing flow rate due to the improved SO₂ retention time. The elemental mapping confirmed the uniform distribution of sulfur species over the oxide surface. X-ray diffraction showed the absence of metal sulfate nanoparticles in the SO₂-exposed samples. The X-ray photoelectron analysis confirmed the formation of surface sulfate and bisulfate. The formation of oxidized sulfur species was mediated by hydroxyl groups over NMO and lattice oxygen over NCO. Thus, the work demonstrated here is the first such report on the use of NaM_xO_y-type materials for SO₂ mineralization.

Size-controlled, hollow and hierarchically porous Co2Ni2 alloy nanocubes for efficient oxygen reduction in microbial fuel cells

Schematic illustration of the fabrication of CoxNiy alloy nanocubes (ANCs) and hollow CoxNiy alloy nanocubes (HANCs).

From MOF-199 Microrods to CuO Nanoparticles for Room-Temperature Desulfurization: Regeneration and Repurposing Spent Adsorbents as Sustainable Approaches

MOF-199 is one of the well-studied metal-organic frameworks (MOFs) for the capture of small gas molecules. In this study, we have investigated the thermal transformation of MOF-199 microrods to CuO nanoparticles by various microscopic and spectroscopic techniques. The growth of oxide was initiated by the formation of ∼2.5 nm particles at 200 °C, which ended up as CuO nanoparticles of ∼100-250 nm size at 550 °C. An intermediate presence of Cu2O along with CuO was recorded at 280 °C. The MOF and calcined products were tested for the room-temperature desulfurization process. MOF-199 showed the maximum adsorption capacity for H2S gas (77.1 mg g-1) among all adsorbents studied. Also, MOF-199 showed a better regeneration efficiency than the derived oxide. For a sustainable process, the exhausted adsorbents were used for the photocatalytic degradation of methylene blue. The exhausted materials showed better degradation efficiencies than the fresh materials. This study reports new sustainable approaches for MOF-199 application in air and water decontamination.

Bimetallic Ag–Cu-trimesate metal–organic framework for hydrogen sulfide removal

Bimetallic Ag-Cu-trimesate metal-organic framework was fabricated for H2S mineralization. The MOF was partially regenerated using H2O2 solution for five cycles.