Characterization of Chemisorbed Species and Active Adsorption Sites in Mg-Al Mixed Metal Oxides for High-Temperature CO2 Capture

Fully Biobased Degradable Vitrimer Foams: Mechanical Robust, Catalyst-Free Self-Healing, and Shape Memory Properties

Thermosetting foams have limited capabilities for recycling, reprocessing, or reshaping. Moreover, most of the foaming agents currently employed in these foams are derived from organic compounds sourced from petrochemicals, thereby posing a significant environmental threat due to heightened pollution. To solve these problems, a fully biobased degradable vitrimer foam (EPC-X) was fabricated using an environmentally friendly all-in-one foaming strategy by cross-linking epoxidized malepimaric anhydride (EMPA), 1,5-diaminopentane (PDA), and 1,5-diaminopentane carbamate (PDAC) as a latent curing-blowing agent. To our delight, the vitrimer foams exhibit excellent mechanical properties (2.86 ± 0.11 MPa compressive strength) owing to their unique rigid rosin backbone and cross-linking networks. The presence of dynamic β-hydroxy ester bonds and the self-catalytic behavior of tertiary amine groups facilitate network rearrangement without requiring additional catalysts, thereby resulting in the development of EPC-X with rapid self-healing and shape memory properties. The self-healing foam could support a weight of 500 g (approximately 562 times its own mass). Moreover, these high-performance vitrimer foams can also be easily degraded in an ethanolamine (EA) or NaOH solution under mild conditions. Such a design strategy offers an alternative approach for developing superior degradable and thermal stimuli-responsive thermosetting foams.

Innovative Strategy for Truly Reversible Capture of Polluting Gases-Application to Carbon Dioxide

This paper consists of a deep analysis and data comparison of the main strategies undertaken for achieving truly reversible capture of carbon dioxide involving optimized gas uptakes while affording weakest retention strength. So far, most strategies failed because the estimated amount of CO2 produced by equivalent energy was higher than that captured. A more viable and sustainable approach in the present context of a persistent fossil fuel-dependent economy should be based on a judicious compromise between effective CO2 capture with lowest energy for adsorbent regeneration. The most relevant example is that of so-called promising technologies based on amino adsorbents which unavoidably require thermal regeneration. In contrast, OH-functionalized adsorbents barely reach satisfactory CO2 uptakes but act as breathing surfaces affording easy gas release even under ambient conditions or in CO2-free atmospheres. Between these two opposite approaches, there should exist smart approaches to tailor CO2 retention strength even at the expense of the gas uptake. Among these, incorporation of zero-valent metal and/or OH-enriched amines or amine-enriched polyol species are probably the most promising. The main findings provided by the literature are herein deeply and systematically analysed for highlighting the main criteria that allow for designing ideal CO2 adsorbent properties.

Unravelling the effect of paramagnetic Ni2+ on the 13C NMR shift tensor for carbonate in Mg2-xNixAl layered double hydroxides by quantum-chemical computations

Structural disorder and low crystallinity render it challenging to characterise the atomic-level structure of layered double hydroxides (LDH). We report a novel multi-step, first-principles computational workflow for the analysis of paramagnetic solid-state NMR of complex inorganic systems such as LDH, which are commonly used as catalysts and energy storage materials. A series of 13CO32--labelled Mg2-xNixAl-LDH, x ranging from 0 (Mg2Al-LDH) to 2 (Ni2Al-LDH), features three distinct eigenvalues δ11, δ22 and δ33 of the experimental 13C chemical shift tensor. The δii correlate directly with the concentration of the paramagnetic Ni2+ and span a range of |δ11 - δ33| ≈ 90 ppm at x = 0, increasing to 950 ppm at x = 2. In contrast, the isotropic shift, δiso(13C), only varies by -14 ppm in the series. Detailed insight is obtained by computing (1) the orbital shielding by periodic density-functional theory involving interlayer water, (2) the long-range pseudocontact contribution of the randomly distributed Ni2+ ions in the cation layers (characterised by an ab initio susceptibility tensor) by a lattice sum, and (3) the close-range hyperfine terms using a full first-principles shielding machinery. A pseudohydrogen-terminated two-layer cluster model is used to compute (3), particularly the contact terms. Due to negative spin density contribution at the 13C site arising from the close-by Ni2+ sites, this step is necessary to reach a semiquantitative agreement with experiment. These findings influence future NMR investigations of the formally closed-shell interlayer species within LDH, such as the anions or water. Furthermore, the workflow is applicable to a variety of complex materials.

Mg-O-F Nanocomposite Catalysts Defend against Global Warming via the Efficient, Dynamic, and Rapid Capture of CO2 at Different Temperatures under Ambient Pressure

The utilization of Mg-O-F prepared from Mg(OH)₂ mixed with different wt % of F in the form of (NH₄F·HF), calcined at 400 and 500 °C, for efficient capture of CO₂ is studied herein in a dynamic mode. Two different temperatures were applied using a slow rate of 20 mL·min^-1 (100%) of CO₂ passing through each sample for only 1 h. Using the thermogravimetry (TG)-temperature-programed desorption (TPD) technique, the captured amounts of CO₂ at 5 °C were determined to be in the range of (39.6-103.9) and (28.9-82.1) mg_CO2 ·g^-1 for samples of Mg(OH)₂ mixed with 20-50% F and calcined at 400 and 500 °C, respectively, whereas, at 30 °C, the capacity of CO₂ captured is slightly decreased to be in the range of (32.2-89.4) and (20.9-55.5) mg_CO2 ·g^-1, respectively. The thermal decomposition of all prepared mixtures herein was examined by TG analysis. The obtained samples calcined at 400 and 500 °C were characterized by X-ray diffraction and surface area and porosity measurements. The total number of surface basic sites and their distribution over all samples was demonstrated using TG- and differential scanning calorimetry-TPD techniques using pyrrole as a probe molecule. Values of (ΔH) enthalpy changes corresponding to the desorption steps of CO₂ were calculated for the most active adsorbent in this study, that is, Mg(OH)₂ + 20% F, at 400 and 500 °C. This study's findings will inspire the simple preparation and economical design of nanocomposite CO₂ sorbents for climate change mitigation under ambient conditions.