The effect of pore size dimensions in isoreticular zeolites on carbon dioxide adsorption heats

Enhancing Iodine Capture of Porous Organic Cages through N-Heteroatom Engineering

Iodine radioisotopes, produced or released during nuclear-related activities, severely affect human health and the environment. The efficient removal of radioiodine from both aqueous and vapor phases is crucial for the sustainable development of nuclear energy. In this study, we propose an "N-heteroatom engineering" strategy to design three porous organic cages with N-containing functional groups for efficient iodine capture. Among the molecular cages investigated, FT-Cage incorporating tertiary amine groups and RT-Cage with secondary amine groups show higher adsorption capacity and much faster iodine release compared to IT-Cage with imine groups. Detailed investigations demonstrate the superiority of amine groups, along with the influence of crystal structures and porosity, for iodine capture. These findings provide valuable insights for the design of porous organic cages with enhanced capabilities for capturing iodine.

Synergy of developed micropores and electronic structure defects in carbon-doped boron nitride for CO2 capture

With the aim of relieving the serious environmental and climate issues arising from excessive emission of anthropogenic CO₂, extensive solid absorbents have been developed for CO₂ capture. Among them, porous boron nitride (BN) is considered an ideal candidate due to its high specific surface area, abundant structural defects, low density, and outstanding chemical inertness. Herein, BN absorbents were synthesized from pyrolysis of melamine-boric acid precursors, and the effect of pyrolysis temperature (900, 1000, 1050 and 1100 °C) on the properties and performances was investigated. Various characterizations were performed to evaluate the physicochemical properties and CO₂ uptake capacities of BN absorbents. The result demonstrated that a carbon-doped BN structure was achieved instead of a pure BN material, and the carbonization degree was enhanced with the increase of pyrolysis temperatures. BN absorbent pyrolyzed at 1100 °C exhibited the highest CO₂ adsorption capacity of 3.71 mmol/g (273 K). The reason should be that the doping of carbon in the framework of BN contributed to the formation of abundant micropores, which enhanced the physical adsorption by offering more adsorption sites. At the same time, more negative charges on BN were induced by structural defects, which favored the chemical adsorption of CO₂ by invoking charge-induced chemisorption interaction. This study clarified the role of pore structure and electronic structure defects in CO₂ adsorption capacity of carbon-doped BN, which would open up more spacious avenues for the development of promising BN-based absorbents, or even catalysts.

Achieving High-Selective CO2 Adsorption on SAPO-35 Zeolites by Template-Modulating Framework Silicon Content

Small-pore silicoaluminophosphate (SAPO) zeolites with 8-ring pore windows and appropriate acidities/polarities, for example, SAPO-34 (CHA) and SAPO-56 (AFX) have proven as potential adsorbing materials for selective adsorption of CO2. However,...

Synthesis and Post-Synthesis Transformation of Germanosilicate Zeolites

Zeolites are one of the most important heterogeneous catalysts, with a high number of large-scale industrial applications. While the synthesis of new zeolites remain rather limited, introduction of germanium has substantially increased our ability to not only direct the synthesis of zeolites but also to convert them into new materials post-synthetically. The smaller Ge-O-Ge angles (vs. Si-O-Si) and lability of the Ge-O bonds in aqueous solutions account for this behaviour. This Minireview discusses critical aspects of germanosilicate synthesis and their post-synthesis transformations to porous materials.

Microstructure, Thermal Stability, and Catalytic Activity of Compounds Formed in CaO-SiO2-Cr(NO3)3-H2O System

In this work, the thermal stability, microstructure, and catalytic activity in oxidation reactions of calcium silicate hydrates formed in the CaO-SiO2-Cr(NO3)3-H2O system under hydrothermal conditions were examined in detail. Dry primary mixture with a molar ratio of CaO/SiO2 = 1.5 was mixed with Cr(NO3)3 solution (c = 10 g Cr3+/dm3) to reach a solution/solid ratio of the suspension of 10.0:1. Hydrothermal synthesis was carried out in unstirred suspensions at 175 °C for 16 h. It was determined that, after treatment, semicrystalline calcium silicate hydrates C-S-H(I) and/or C-S-H(II) with incorporated Cr3+ ions (100 mg/g) were formed. The results of in situ X-ray diffraction and simultaneous thermal analyses showed that the products were stable until 500 °C, while, at higher temperatures, they recrystallized to calcium chromate (CaCrO4, 550 °C) and wollastonite (800-850 °C). It was determined that both the surface area and the shape of the dominant pore changed during calcination. Propanol oxidation experiments showed that synthetic semicrystalline calcium silicate hydrates with intercalated chromium ions are able to exchange oxygen during the heterogeneous oxidation process. The obtained results were confirmed by XRD, STA, FT-IR, TEM, SEM, and BET methods, and by propanol oxidation experiments.

CO2 and water vapor adsorption properties of framework hybrid W-ZSM-5/silicalite-1 prepared from RHA

Framework hybrid W-ZSM-5 and W-silicalite-1 zeolites were synthesized by hydrothermal methods using rice husk ash (RHA) as a silicon raw material. RHA is a low-cost precursor material, and its use can also alleviate the environmental and human health related problems that may occur when it is stacked in open fields. A series of comparative samples were characterized by XRD, FTIR, ICP-OES, SEM, N₂ adsorption–desorption and pore size analysis in order to examine their crystal structure, hybrid state, morphology and textural properties. The maximum CO₂ adsorption capacities of W-ZSM-5 and W-silicalite-1 are 81.69 and 69.96 cm³ g⁻¹, respectively, measured at 15 bar. The isotherms of CO₂, N₂ and O₂ are perfectly fitted by the Toth model, and it is noted that the presence of Al atoms increases the heterogeneity. It can be seen that the greater the heterogeneity of the adsorbent, the larger the CO₂ adsorption capacity achieved. The incorporation of tungsten into the framework does not affect the crystallization of the zeolite, but it prevents the formation of silanol and O–H groups at the adsorption sites. Therefore, the CO₂/H₂O selectivity of W-ZSM-5 is slightly higher than that of ZSM-5, and that of W-silicalite-1 is three times that of silicalite-1. W-ZSM-5/silicalite-1 are promising adsorbents for separating CO₂ under humid industrial conditions.

Framework hybrid W-ZSM-5 and W-silicalite-1 zeolites were synthesized by hydrothermal methods using rice husk ash (RHA) as a silicon raw material.

Industrial carbon dioxide capture and utilization: state of the art and future challenges

This review covers the sustainable development of advanced improvements in CO₂ capture and utilization.

Synthesis and Characterization of Aminosilane Grafted Cellulose Nanocrystal Modified Formaldehyde-Free Decorative Paper and its CO2 Adsorption Capacity

As one of the main consumables of interior decoration and furniture, decorative paper can be seen everywhere in the indoor space. However, because of its high content of formaldehyde, it has a certain threat to people’s health. Therefore, it is necessary to develop and study new formaldehyde-free decorative paper to meet the market demand. In this work, we have obtained formaldehyde-free decorative paper with high CO₂ adsorption capacity. Here, cellulose nanocrystals (CNC) were prepared by hydrolyzing microcrystalline cellulose with sulfuric acid. The N-(2-aminoethyl) (3-amino-propyl) methyldimethoxysilane (AEAPMDS) was grafted onto the CNCs by liquid phase hydrothermal treatment, and the aqueous solution was substituted by tert-butanol to obtain aminated CNCs (AEAPMDS-CNCs). The as-prepared AEAPMDS-CNCs were applied to formaldehyde-free decorative paper by the spin-coating method. The effects of various parameters on the properties of synthetic materials were systematically studied, and the optimum reaction conditions were revealed. Moreover, the surface bond strength and abrasion resistance of modified formaldehyde-free decorative paper were investigated. The experimental results showed that AEAPMDS grafted successfully without destroying the basic morphology of the CNCs. The formaldehyde-free decorative paper coated with AEAPMDS-CNCs had high CO₂ adsorption capacity and exhibited excellent performance of veneer to plywood. Therefore, laminating the prepared formaldehyde-free decorative paper onto indoor furniture can achieve the purpose of capturing indoor CO₂ and have a highly potential use for the indoor decoration.

Enhancing CO2 Adsorption and Separation Properties of Aluminophosphate Zeolites by Isomorphous Heteroatom Substitutions

Mg, Co-substituted aluminophosphate zeolites with ERI framework topology (denoted as MgAPO-ERI and CoAPO-ERI) have been synthesized under hydrothermal conditions by using N, N, N', N'-tetramethyl-1,6-hexanediamine as organic template. Their CO₂ adsorption properties are investigated in comparison to those of the pure aluminophosphate counterpart AlPO-ERI. CoAPO-ERI shows the highest CO₂ uptake of 57.3 cm³ g^-1 (273 K and 1 bar) and the highest isosteric heat of 39.0 kJ mol^-1 among the three samples. Importantly, the incorporation of Mg²⁺ and Co²⁺ ions in the framework of AlPO-ERI can greatly improve the adsorption selectivities of CO₂ over CH₄ and N₂. Whereafter, transient breakthrough simulations were investigated and further proved the advantages of heteroatoms for separations. These results demonstrate that isomorphous heteroatom substitutions in aluminophosphate zeolites play a key role in enhancing CO₂ adsorption and separation abilities.