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Amine-functionalized porous solid materials are effective sorbents for direct air capture (DAC) of CO 2 . However, they are prone to oxidative degradation in service, increasing the materials cost for widespread implementation. While the identification of oxidation products has given insights into degradation pathways, the roles of some species, like CO 2 itself, remain unresolved, with conflicting information in the literature. Here, we investigate the impact of CO 2 on the oxidative degradation of poly(ethylenimine)-alumina (PEI/Al 2 O 3 ) sorbents under conditions encompassing a wide range of CO 2 -air mixture compositions and temperatures relevant to DAC conditions, thereby reconciling the conflicting data in the literature. Degradation profiles characterized by thermogravimetric analysis, in situ ATR-FTIR, and CO 2 capacity measurements reveal nonmonotonic effects of CO 2 concentrations and temperatures on oxidation kinetics. Specifically, 0.04% CO 2 accelerates PEI/Al 2 O 3 oxidation more at low temperatures (<90 °C) compared to 1% and 5% CO 2 , but this trend reverses at high temperatures (>90 °C). First-principles metadynamics, machine learning accelerated molecular dynamics simulations, and 1 H relaxometry experiments show that chemisorbed CO 2 acid-catalyzes critical oxidation reactions, while extensive CO 2 uptake reduces PEI branch mobility, slowing radical propagation. These contrasting kinetic effects of CO 2 explain the complex degradation profiles observed in this work and in prior literature. Collectively, this work highlights the importance of considering atmospheric components in the design of DAC sorbents and processes. Additionally, it identifies the unconstrained branch mobility and local acid environment as two of the major culprits in the oxidation of amine-based sorbents, suggesting potential strategies to mitigate sorbent degradation.

This study investigates the effects of elevated temperature thermal treatments on the direct air capture of CO 2 by aminosilane-grafted SBA-15 silica sorbents. Exposing samples to high temperatures (200-250 °C compared to 80-120 °C) in an inert environment resulted in improved CO 2 capacity (5-21%) that was sustained over multiple adsorption/desorption cycles.

Free energy sampling, deep potential molecular dynamics, and characterizations provide insights into the impact of epoxide-functionalization on the hydrogen bonding and mobility of poly(ethylenimine), a promising CO 2 sorbent. These findings rationalize the anti-degradation effects of epoxide functionalization and open up new avenues for designing more durable CO 2 sorbents.

The diffusion processes between adsorbent and adsorbate naturally play a significant role in the efficiency and selectivity of the heterogenous catalytic process. This paper considers the importance of diffusion processes in the transfer hydrogenation reaction of levulinic acid to γ-valerolactone by MIL-88B, MIL-100, and ZIF8@Pd monolithic catalysts. Over a period of five catalytic cycles, it was shown that the Fe-based catalysts can achieve similar conversions to the ZIF-8 supported Pd, with the only current limitation being the lower aqueous stability of these MOFs. Diffusion constants were calculated using the ZLC method, with micropore diffusion limitation found for ZIF-8 and MIL-100 monolithic frameworks at 2.7 x 10 -8 and 4.6 x 10 -8  cm 2  s -1 respectively. This diffusion limitation was also confirmed by IR spectroscopy with an increasing concentration of C-H bands on the MOF substrate post-reaction. Mass transfer coefficients, also calculated by ZLC, revealed increased mass transport for the hydrophobic ZIF-8 framework, which perhaps aids in the γ-valerolactone selectivity over side products that are produced in the absence of catalytic material, as seen for MIL-88B and MIL-100 after multiple uses., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 McIntyre, Saenz-Cavazos, Hunter-Sellars, Williams.)

Redox flow batteries using aqueous organic-based electrolytes are promising candidates for developing cost-effective grid-scale energy storage devices. However, a significant drawback of these batteries is the cross-mixing of active species through the membrane, which causes battery performance degradation. To overcome this issue, here we report size-selective ion-exchange membranes prepared by sulfonation of a spirobifluorene-based microporous polymer and demonstrate their efficient ion sieving functions in flow batteries. The spirobifluorene unit allows control over the degree of sulfonation to optimize the transport of cations, whilst the microporous structure inhibits the crossover of organic molecules via molecular sieving. Furthermore, the enhanced membrane selectivity mitigates the crossover-induced capacity decay whilst maintaining good ionic conductivity for aqueous electrolyte solution at pH 9, where the redox-active organic molecules show long-term stability. We also prove the boosting effect of the membranes on the energy efficiency and peak power density of the aqueous redox flow battery, which shows stable operation for about 120 h (i.e., 2100 charge-discharge cycles at 100 mA cm -2 ) in a laboratory-scale cell., (© 2022. The Author(s).)

The variation in pore size in mesoporous films produced by electrochemically assisted self-assembly (EASA) with the surfactant chain length is described. EASA produces a hexagonal array of pores perpendicular to the substrate surface by using an applied potential to organize cationic surfactants and the resultant current to drive condensation in a silica sol. Here, we show that a range of pore sizes between 2 and 5 nm in diameter is available with surfactants of the form [Me 3 NC n H 2 n +1 ]Br, with alkyl chain lengths between C 14 and C 24 . The film quality, pore order, pore size, and pore accessibility are probed with a range of techniques.

The conservation of cellulose acetate plastics in museum collections presents a significant challenge, due to the material's instability. Several studies have led to an understanding of the role of relative humidity (RH) and temperature in the decay process. It is well established that a major decay mechanism in cellulose acetate museum objects is the loss of plasticiser, and that the main decay mechanism of the polymer chain involves hydrolysis reactions. This leads to the loss of sidechain groups and the breakdown of the main polymer backbone. However, interactions between these decay mechanisms, specifically the way in which the loss of plasticiser can modify the interaction between cellulose acetate and water, has not yet been investigated. This research addresses the role of RH, studying the sorption and diffusion of water in cellulose acetate and how this interaction can be affected by plasticiser concentration using Dynamic Vapour Sorption (DVS)., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Carbon capture utilisation and storage (CCUS) using solid sorbents such as zeolites, activated carbon and Metal-Organic Frameworks (MOFs) could facilitate the reduction of anthropogenic CO 2 concentration. Developing efficient and stable adsorbents for CO 2 capture as well as understanding their transport diffusion limitations for CO 2 utilisation plays a crucial role in CCUS technology development. However, experimental data available on CO 2 capture and diffusion under relevant industrial conditions is very limited, particularly for MOFs. In this study we explore the use of a gravimetric Dynamic Vapour Sorption (DVS) instrument to measure low concentration CO 2 uptake and adsorption kinetics on a novel partially fluorinated MIL-101(Cr) saturated with different water vapour concentrations, at ambient pressure and temperature. Results show that up to water P / P 0 = 0.15 the total CO 2 uptake of the modified material improves and that the introduction of small amounts of water enhances the diffusion of CO 2 . MIL-101(Cr)-4F(1%) proved to be a stable material under moist conditions compared to other industrial MOFs, allowing facile regeneration under relevant industrial conditions., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

Liquid-in-liquid droplets are typically generated by the partitioning of immiscible fluids, e.g. by mechanical shearing with macroscopic homogenisers or microfluidic flow focussing. In contrast, partially miscible liquids with a critical solution temperature display a temperature-dependent mixing behaviour. In this work, we demonstrate how, for a blend of methanol (MeOH) and the thermotropic liquid crystal (LC) 4-Cyano-4'-pentylbiphenyl (5CB), cooling from a miscible to an immiscible state allows the controlled formation of microdroplets. A near-room-temperature-induced phase separation leads to nucleation, growth and coalescence of mesogen-rich droplets. The size and number of the droplets is tunable on the microscopic scale by variation of temperature quench depth and cooling rate. Further cooling induces a phase transition to nematic droplets with radial configuration, well-defined sizes and stability over the course of an hour. This temperature-induced approach offers a scalable and reversible alternative to droplet formation with relevance in diagnostics, optoelectronics, materials templating and extraction processes.