Semiconducting Metal Oxide Based Sensors for Selective Gas Pollutant Detection

A review of some papers published in the last fifty years that focus on the semiconducting metal oxide (SMO) based sensors for the selective and sensitive detection of various environmental pollutants is presented

Influence of Density and Water Content on The Thermal Diffusivity of Wood Chips

The use of agro-industrial residues are currently experiencing an undeniable revival of interest in developing fully renewable insulation materials, that can be competitive in price and performance, in addition of low embodied energy. Among these vegetable waste materials; wood chips. These latter are light, compressible and very sensitive to water, due to their highly porous structure, which constantly modifies their thermal properties. The main objective of this study is to examine the influence of moisture content and density on the thermal diffusivity of wood chips, using the flash method. Four theoretical models were used to identify the thermal diffusivity. The results obtained show a decrease in thermal diffusivity with an increase in wood chips density. Furthermore, moisture content has an influence on thermal diffusivity. The experimental results show fluctuations with a slight decrease in thermal diffusivity with a maximum corresponding to a moisture content value Wm

Recent Progress in Metal-Organic Framework-Derived Chalcogenides (MX; X = S, Se) as Electrode Materials for Supercapacitors and Catalysts in Fuel Cells

Supercapacitors (SCs) are recognized by high power densities and significantly higher cyclic stability compared to batteries. However, the energy density in SCs should be improved for better applications and commercialization. This could be achieved by developing materials characterized by such porous structures as metal-organic frameworks (MOFs) and metal chalcogenides in the electrodes’ materials. Herein, the recent advances in MOF derived from metal sulfides and selenides as electrode materials for SCs are reviewed and discussed. Strategies such as adopting core-shell structures, carbon-coating, and doping, which are used to promote the electrochemical performances of these MOF-based materials, are presented. Additionally, the progress in developing S-doped MOF-derived catalysts for the oxidation-reduction reaction (ORR) in the cathode of fuel cells is also reviewed. In addition, the challenges and future research trends are summarized in this minireview

Systematic Postsynthetic Modification of Nanoporous Organic Frameworks for Enhanced CO₂ Capture from Flue Gas and Landfill Gas

Controlled postsynthetic nitration of NPOF-1, a nanoporous organic framework constructed by nickel(0)-catalyzed Yamamoto coupling of 1,3,5-tris­(4-bromophenyl)­benzene, has been performed and is proven to be a promising route to introduce nitro groups and to convert mesopores to micropores without compromising surface area. Reduction of the nitro groups yields aniline-like amine-functionalized NPOF-1-NH₂ that has a micropore volume of 0.48 cm³ g^–1, which corresponds to 71% of the total pore volume and a Brunauer–​Emmett–​Teller surface area of 1535 m² g^–1. Adequate basicity of the amine functionalities leads to modest isosteric heats of adsorption for CO₂, which allow for high regenerability. The unique combination of high surface area, microporous structure, and amine-functionalized pore walls enables NPOF-1-NH₂ to have remarkable CO₂ working capacity values for removal from landfill gas and flue gas. The performance of NPOF-1-NH₂ in CO₂ removal ranks among the best by porous organic materials

Simultaneous Adsorption and Reduction of Cr(VI) to Cr(III) in Aqueous Solution Using Nitrogen-Rich Aminal Linked Porous Organic Polymers

Two novel nitrogen-rich aminal linked porous organic polymers, NRAPOP-O and NRAPOP-S, have been prepared using a single step-one pot Schiff-base condensation reaction of 9,10-bis-(4,6-diamino-S-triazin-2-yl)benzene and 2-furaldehyde or 2-thiophenecarboxaldehyde, respectively. The two polymers show excellent thermal and physiochemical stabilities and possess high porosity with Brunauer–Emmett–Teller (BET) surface areas of 692 and 803 m2 g−1 for NRAPOP-O and NRAPOP-S, respectively. Because of such porosity, attractive chemical and physical properties, and the availability of redox-active sites and physical environment, the NRAPOPs were able to effectively remove Cr(VI) from solution, reduce it to Cr(III), and simultaneously release it into the solution. The efficiency of the adsorption process was assessed under various influencing factors such as pH, contact time, polymer dosage, and initial concentration of Cr(VI). At the optimum conditions, 100% removal of Cr(VI) was achieved, with simultaneous reduction and release of Cr(III) by NRAPOP-O with 80% efficiency. Moreover, the polymers can be easily regenerated by the addition of reducing agents such as hydrazine without significant loss in the detoxication of Cr(VI)

Simultaneous Adsorption and Reduction of Cr(VI) to Cr(III) in Aqueous Solution Using Nitrogen-Rich Aminal Linked Porous Organic Polymers

Two novel nitrogen-rich aminal linked porous organic polymers, NRAPOP-O and NRAPOP-S, have been prepared using a single step-one pot Schiff-base condensation reaction of 9,10-bis-(4,6-diamino-S-triazin-2-yl)benzene and 2-furaldehyde or 2-thiophenecarboxaldehyde, respectively. The two polymers show excellent thermal and physiochemical stabilities and possess high porosity with Brunauer–Emmett–Teller (BET) surface areas of 692 and 803 m2 g−1 for NRAPOP-O and NRAPOP-S, respectively. Because of such porosity, attractive chemical and physical properties, and the availability of redox-active sites and physical environment, the NRAPOPs were able to effectively remove Cr(VI) from solution, reduce it to Cr(III), and simultaneously release it into the solution. The efficiency of the adsorption process was assessed under various influencing factors such as pH, contact time, polymer dosage, and initial concentration of Cr(VI). At the optimum conditions, 100% removal of Cr(VI) was achieved, with simultaneous reduction and release of Cr(III) by NRAPOP-O with 80% efficiency. Moreover, the polymers can be easily regenerated by the addition of reducing agents such as hydrazine without significant loss in the detoxication of Cr(VI)

Pyrene Bearing Azo-Functionalized Porous Nanofibers for CO2 Separation and Toxic Metal Cation Sensing

This article describes the construction of a novel luminescent azo-linked polymer from 1,3,6,8-tetra(4--aminophenyl)pyrene using a copper(I)-catalyzed oxidative homocoupling reaction

Nitrogen-Rich Porous Polymers for Carbon Dioxide and Iodine Sequestration for Environmental Remediation

The use of fossil fuels for energy production is accompanied by carbon dioxide release into the environment causing catastrophic climate changes. Meanwhile, replacing fossil fuels with carbon-free nuclear energy has the potential to release radioactive iodine during nuclear waste processing and in case of a nuclear accident. Therefore, developing efficient adsorbents for carbon dioxide and iodine capture is of great importance. Two nitrogen-rich porous polymers (NRPPs) derived from 4-bis-(2,4-diamino-1,3,5-triazine)-benzene building block were prepared and tested for use in CO₂ and I₂ capture. Copolymerization of 1,4-bis-(2,4-diamino-1,3,5-triazine)-benzene with terephthalaldehyde and 1,3,5-tris­(4-formylphenyl)­benzene in dimethyl sulfoxide at 180 °C afforded highly porous NRPP-1 (SA_BET = 1579 m² g^–1) and NRPP-2 (SA_BET = 1028 m² g^–1), respectively. The combination of high nitrogen content, π-electron conjugated structure, and microporosity makes NRPPs very effective in CO₂ uptake and I₂ capture. NRPPs exhibit high CO₂ uptakes (NRPP-1, 6.1 mmol g^–1 and NRPP-2, 7.06 mmol g^–1) at 273 K and 1.0 bar. The 7.06 mmol g^–1 CO₂ uptake by NRPP-2 is the second highest value reported to date for porous organic polymers. According to vapor iodine uptake studies, the polymers display high capacity and rapid reversible uptake release for I₂ (NRPP-1, 192 wt % and NRPP-2, 222 wt %). Our studies show that the green nature (metal-free) of NRPPs and their effective capture of CO₂ and I₂ make this class of porous materials promising for environmental remediation

Effective Approach for Increasing the Heteroatom Doping Levels of Porous Carbons for Superior CO₂ Capture and Separation Performance

Development of efficient sorbents for carbon dioxide (CO₂) capture from flue gas or its removal from natural gas and landfill gas is very important for environmental protection. A new series of heteroatom-doped porous carbon was synthesized directly from pyrazole/KOH by thermolysis. The resulting pyrazole-derived carbons (PYDCs) are highly doped with nitrogen (14.9–15.5 wt %) as a result of the high nitrogen-to-carbon ratio in pyrazole (43 wt %) and also have a high oxygen content (16.4–18.4 wt %). PYDCs have a high surface area (SA_BET = 1266–2013 m² g^–1), high CO₂ <i>Q</i>_st (33.2–37.1 kJ mol^–1), and a combination of mesoporous and microporous pores. PYDCs exhibit significantly high CO₂ uptakes that reach 2.15 and 6.06 mmol g^–1 at 0.15 and 1 bar, respectively, at 298 K. At 273 K, the CO₂ uptake improves to 3.7 and 8.59 mmol g^–1 at 0.15 and 1 bar, respectively. The reported porous carbons also show significantly high adsorption selectivity for CO₂/N₂ (128) and CO₂/CH₄ (13.4) according to ideal adsorbed solution theory calculations at 298 K. Gas breakthrough studies of CO₂/N₂ (10:90) at 298 K showed that PYDCs display excellent separation properties. The ability to tailor the physical properties of PYDCs as well as their chemical composition provides an effective strategy for designing efficient CO₂ sorbents