Vapor Sorption Research Articles

Development of New Composite Beds for Enhancing the Heat Transfer in Adsorption Cooling Systems

Adsorption chillers are distinguished by their low electricity consumption, lack of moving parts and exceptional reliability. However, their considerable weight, due to the low sorption capacity of conventional adsorbents, remains a key limitation. This study investigates the effect of introducing thermally conductive additives—aluminium powder, copper powder and graphite flakes—at 5, 15 and 25 wt.% to silica-gel-based adsorbent beds on the enhancement of heat transfer. In contrast to other works, this study also includes a novel analysis of the thermal properties of dry sorbents, since the moisture content affects the thermal conductivity. Additives improve the thermal conductivity, as measured by the laser flash method (LFA), of the bed by up to 20.7% while maintaining a reasonable sorption capacity, as measured by the dynamic vapor sorption (DVS). Additions of copper at 5–15 wt.% and graphite flakes at 15–25 wt.% provide an optimal compromise between thermal conductivity and sorption capacity. Aluminium powder, on the other hand, offers flexibility over a wider range (5–25 wt.%). The increased thermal conductivity of these modified materials is expected to lead to more efficient heat transport, which suggests the hypothesis that it could reduce the cycle time and increase the efficiency of adsorption chillers.

Microencapsulation using spray drying of anthoxyanins from Lannea microcarpa (African grape) fruits juice with pyrodextrin from sweet potato starch

Anthocyanins rich fruits of Lannea microcarpa (African grape) with antioxidant activity are an important food and herbal medicine in central Africa. This study sought to use response surface methodology to optimize spray drying microencapsulation of anthocyanins from L. microcarpa fruit juice, examining the influence of inlet air temperature (120—150 °C), inlet air flow rate (60—80 m3/h) and carrier agent (pyrodextrin) concentration (8 -16 g/100 g of juice), on various spray-dried powders characteristics. Moreover, the thermal stability study of L. microcarpa fruit juice powder produced at optimal process conditions was studied. The linear effect of inlet air temperature, inlet air flow rate and carrier agent concentration significantly affected the fruit powder properties (Moisture content, hygroscopicity, encapsulation efficiency) (P < 0.05), except in the case of hygroscopicity where linear effect of inlet air temperature did not. The optimum spray drying conditions to obtain the encapsulated fruit juice powder were determined as 150°C inlet air temperature, 80 m3/h inlet air flow rate and 9 g/100 g carrier agent concentration. The optimal spray dried juice powder was produced with a product yield of 72.4%, water activity of 0.281, having a poor flowability but high cohesiveness. Dynamic Vapor Sorption analysis showed sorption isotherm fitted GAB and BET models well and lower water activity (aw < 0.5) at 25 °C could be favorable for storage of L. microcarpa powders. Additionally, the stability study shown according to the degradation rate obtained that encapsulated fruit juice powder stored at 25 C exhibited greater stability with rate constant k = 0.0018 day-1 significantly lower than the same spray dried L. microcarpa juice powder stored at 35°C (k = 0.0035 day-1) (p < 0.05). These results demonstrate microencapsulation through spray drying using pyrodextrin from sweet potato was feasible for enhancing the stabilization of anthocyanins in form of powder with potential application in food and chemical industries.Graphical

A Homeostatic Photonic Device Integrating Vapor‐Regulated Thermo‐Optical Feedback Mechanisms

AbstractSelf‐adaptation and homeostasis are features that distinguish living systems from artificial materials. Living systems, such as plants or the human eye, integrate positive and negative feedback mechanisms to autonomously manage their thermal, optical, and chemical responses to changing sunlight conditions. However, replicating such sophisticated behavior in artificial devices presents a significant challenge. Herein, an inorganic homeostatic device is proposed that integrates both positive and negative feedback mechanisms for adaptive regulation of optical properties, water chemical potential, and local temperature driven by a dynamic change of photonic colors. This device consists of a mesoporous graded one dimensional (1D) photonic crystal, acting as a temperature‐responsive shield, coupled with a photothermal layer. The architecture of the device is designed to harness the temperature‐driven vapor sorption into mesoporous to create the feedback. The lateral gradient of the photonic stop band enables achieving dual feedback across multiple wavelengths by simply shifting the light beam's position. In the presence of light, the thermo‐optical device is able to either amplify or attenuate the optical absorption, reflectivity, and local temperature and dynamically change its structural colors. The structure and performance of the device are characterized using multiple techniques such as Grazing‐Incidence Small‐Angle X‐ray Scattering and time‐resolved hyperspectral microscopy. Importantly, the device is fabricated using solution processing, making it compatible with low‐cost manufacturing and paving the way for the development of adaptive and time‐programmed systems for applications like thermo‐regulating windows, smart filters, programmable meta‐surfaces, vapor sensors, or even optical computing.

Abnormal adsorption properties of the MOF CALF-20 as revealed by water and methanol vapor sorption

Abnormal adsorption properties of the MOF CALF-20 as revealed by water and methanol vapor sorption

Enhancing Water Barriers by Protein-Based Surface Treatments for Cellulose-Based Materials

ABSTRACT The global packaging sector has grown consistently, and the use of sustainable materials, including recycled and biodegradable products, is expected to rise. This study focuses on the potential of producing barriers for water and water in moist air (water vapor) from proteins to protect cellulosic materials. Owing to the specific requirements of packaging materials, the main subject of this research was their barrier and strength properties. The scope of this work includes selecting components and their physicochemical treatment to produce functionalized coatings on sprayed paper and pure films, as well as film-coated samples (paper laminated with film). The following tests were used to estimate the hydrophobic, hygroscopic, and strength properties: Cobb absorption, contact angle testing, dynamic vapor sorption, and dynamic mechanical analysis. In most cases, the spray-coated paper and film-coated samples absorbed less liquid water than untreated paper. Wheat gluten protein was the most effective water barrier. In all variants, the vapor sorption, desorption, and hysteresis effects (or the lack thereof) showed significant differences compared to those of cellulosic materials. All variants of the spray-coated and film-coated samples in the dynamic mechanical analysis showed an increase in the strength properties of the samples in comparison to the untreated paper. The increased humidity caused a significant loss in the mechanical properties of all variants, exceeding the strength loss of the untreated control samples.

Effect of Moisture Sorption and Lactose Type on Tablet Quality: A Hygroscopicity Study between Lactose Powder and Tablets.

Lactose is one of the most commonly used tablet diluents and fillers. However, the moisture sorption of lactose powder could exert detrimental effects on the excipient itself, as well as on the tablet quality. The effects of storage relative humidity (RH) conditions for different grades of lactose powders and tablets on compression behavior and tablet qualities were investigated. Four types of lactose were selected in this study: sieved lactose (Pharmatose 110M), granulated lactose (SuperTab 30GR), anhydrous lactose (SuperTab 21AN), and spray-dried lactose (SuperTab 14SD). These powders and tablets were stored at three RH levels (33, 58, 75%) for a certain period of time before determining their properties. For the moisture-sorbed powder, there was little change in the basic physical properties of lactose powder. Based on the dynamic vapor sorption (DVS) results, the lactose grades determined their hygroscopic properties. The reduction in mechanical strength of lactose powder during storage became less pronounced except for 14SD. But a reduction was observed in the tensile strength (TS) of the 14SD powder from 2.1 to 0.9 MPa after storage at 75% RH for 30 days. The fragmentation of lactose increased with increasing storage humidity. By using multivariate statistical analysis, the similarity and variation of powder properties between 14SD and other types of lactose were visualized. For the moisture-sorbed tablet, the TS became higher and the friability became lower. The TS of lactose tablets exhibited an increase of up to 59.8%. Whether water uptake occurred before or after compression adversely affected tablet disintegration. In conclusion, adverse phenomena during production and storage can be effectively minimized by a better understanding of the effects of moisture sorption on lactose powder and tablets.

The Properties of Damaged Starch Granules: The Relationship Between Granule Structure and Water-Starch Polymer Interactions.

The morphology of wheat starch granules with different damaged starch (DS) content was analyzed using a particle size analyzer and scanning electron microscopy (SEM); the granular structure was studied using FT-IR spectroscopy and X-ray diffraction (XRD); and the granule-water interaction was evaluated by thermogravimetric analysis (TGA) and dynamic vapor sorption (DVS). The increase in the level of DS shifted the population of B-type granules towards larger particle diameters and shifted the population of A-type granules towards smaller particle diameters. The appearance of the surface of the starch-damaged granules was rough and flaky (SEM images). Crystallinity reductions were related to higher mechanical damage levels of the granular structure (FT-IR and XRD). Higher DS increased the liquid-water absorption capacity of the granules. Higher DS was associated with increments in less-bound water proportions and reductions in more strongly bound water proportions and related to reductions in the evaporation temperature of these water populations (TGA analyses). Concerning DVS data, the results suggested that the driving force for water-monolayer attachment to the starch granules decreased as DS increased. Therefore, it was suggested that the changes in granule structure led to a weaker water-starch polymer chain interactions due to the increase in DS. The results contribute to a better understanding of the influence of mechanical damage on the starch granular structure, which could be related to the rheological and thermal behavior of starch-based systems with different DS.

Insight into the Use of Brewers' Spent Grain as a Low-Carbon Aggregate in Building Materials.

This study investigates the use of Brewers' Spent Grains (BSGs) as a sustainable biocomposite building materials, using cornstarch as a biopolymer binder. BSG aggregates are compared with hemp shives, a conventional aggregate known for its thermal properties. Starch is employed as a natural binder in three different formulations to further reduce the carbon footprint of the building material. Considering aggregates, the first formulation contains only BSGs, the second consists of half BSGs and half hemp shives, and the third uses only hemp shives. In addition, morphological analysis using Scanning Electron Microscopy (SEM) is conducted to examine the microstructure and porosity of the raw BSG and hemp shives. Hygrothermal properties are measured using Heat Flow Meter (HFM) and Dynamic Vapor Sorption (DVS) techniques, while mechanical properties are also assessed. Results indicate that the thermal conductivity of the BSG formulation (0.131 W/(m·K)) is double that of the hemp shives formulation (0.067 W/(m·K)), whereas the mixed BSG/hemp shives formulation exhibits a thermal conductivity of 0.106 W/(m·K). However, DVS measurements reveal better hygrothermal properties for the BSG formulation compared to the hemp shives formulation. Lastly, mechanical properties are found to be nearly equivalent across the three formulations. These findings suggest that BSG waste has potential as a viable material for use in construction. Further work on formulation optimization and durability is necessary to fully realize the potential of this waste in promoting a circular economy within the building materials industry.

Porphyrin-Based Aluminum Metal-Organic Framework with Copper: Pre-Adsorption of Water Vapor, Dynamic and Static Sorption of Diethyl Sulfide Vapor, and Sorbent Regeneration.

Metal-organic frameworks (MOFs) are hybrid inorganic-organic 3D coordination polymers with metal sites and organic linkers, which are a "hot" topic in the research of sorption, separations, catalysis, sensing, and environmental remediation. In this study, we explore the molecular mechanism and kinetics of interaction of the new copper porphyrin aluminum metal-organic framework (actAl-MOF-TCPPCu) compound 4 with a vapor of the volatile organic sulfur compound (VOSC) diethyl sulfide (DES). First, compound 4 was synthesized by post-synthetic modification (PSM) of Al-MOF-TCPPH2 compound 2 by inserting Cu2+ ions into the porphyrin ring and characterized by complementary qualitative and quantitative chemical, structural, and spectroscopic analysis. Second, the interaction of compound 4 with DES vapor was analyzed dynamically by the novel method of in situ time-dependent attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy at controlled humidity levels. The sorbent-adsorbate interactions, as analyzed by the shifts in IR peaks, indicate that the bonding includes the hydroxy O-H, carboxylate COO-, and phenyl groups. The kinetics of sorption obeys the Langmuir pseudo-first-order rate law. The pre-adsorption of water vapor by compound 4 at the controlled relative humidity under static (equilibrium) conditions yields the binary stoichiometric adsorption complex (Al-MOF-TCPPCu)1.0(H2O)8.0. The pre-adsorption of water vapor makes the subsequent sorption of DES slower, while the kinetics obey the same rate law. Then, static pre-adsorption of water vapor was followed by static sorption of DES vapor, and the ternary adsorption complex (Al-MOF-TCPPCu)1.0(H2O)8.0(DES)3.8 was obtained. Despite the pre-adsorption of significant amounts of water, the binary complex adsorbs a large amount of DES: ca. 36.6 wt. % (per compound 4). Finally, the ternary complex is facilely regenerated by gentle heating under vacuum. Compound 4 and related MOFs are promising for adsorptive removal of vapor of DES and related VOSCs from dry and humid air.

Water Ageing of Epoxies: Effect of Thermal Oxidation

ABSTRACTEpoxy samples obtained by curing bisphenol A diglycidyl ether with triethylenetetramine are thermally oxidized at 160°C under air. The impact on water sorption is investigated by water uptake recorded by Dynamic Vapor Sorption and the gravimetric method. Experimental data mainly showed that water solubility in epoxies increases due to oxidative degradation, meanwhile, the formation of clustering remains limited. In the investigated ageing conditions, water diffusion obeys Fick's law. Despite a significant chain scission process, water diffusivity in polymer remains constant, possibly in line with the fact that hydroxypropylethers are the driving force of water diffusion and are not degraded during thermal ageing.

Optimization of physicochemical properties of theophylline by forming cocrystals with amino acids.

This study presents the synthesis and characterization of novel cocrystal structures of theophylline (THE) with the amino acids gamma-aminobutyric acid (GABA) and l-arginine (ARG). Despite a large number of reports about THE cocrystals, no crystallographic parameters of cocrystals formed by THE and amino acids have been reported. THE is characterized by low solubility, while amino acids as cocrystal co-formers (CCFs) are increasingly recognized for their high solubility and safety. Consequently, the synthesis of cocrystals with amino acids has garnered considerable research interest. To optimize THE's physicochemical properties, amino acids were chosen as CCFs, resulting in the synthesis of two novel cocrystals: THE-GABA and THE-ARG-2H2O. Comprehensive characterization, such as X-ray diffraction analysis, spectral analysis, thermal analysis, and dynamic vapor sorption were conducted for THE-GABA and THE-ARG-2H2O, alongside stability and solubility assessments. To better explain the characterization and evaluation results, the theoretical calculation methods were adopted, including the molecular electrostatic potential (MESP), topological analysis, energy framework, Hirshfeld surface and crystal voids. The study's findings reveal that the solubility and permeability of THE in both novel cocrystals, THE-GABA and THE-ARG-2H2O, have increased, especially in the latter. Meanwhile, the hygroscopicity of them was at a low level which was basically consistent with THE.

Unveiling the Sorption Properties of Graphene Oxide-M13 Bacteriophage Aerogels for Advanced Sensing and Environmental Applications.

GraPhage13 aerogels (GPAs) are ultralow density, porous structures fabricated through the self-assembly of graphene oxide (GO) and M13 bacteriophage. Given GPA's high surface area and extensive porous network, properties typically associated with highly adsorbent materials, it is essential to characterize its sorption capabilities, with a focus on unlocking its potential for advanced applications in areas such as biomedical sensing and environmental monitoring. Herein, the water, ethanol and acetone sorption properties of GPA were explored using dynamic vapor sorption (DVS). GPA was found to be highly hygroscopic, with a sorption capacity of 0.68 ± 0.02 g/g, double that of conventional desiccant silica gels and 20% higher than GO laminates. This remarkable sorption capacity, along with its sorption kinetics, was influenced by both GPA's morphology and the strong interactions between the water molecules and the functional groups on the GO within GPA. The low hysteresis and stability of GPA during repeated sorption-desorption cycles highlight the reversibility of water sorption. While GPA shows lower capacity for ethanol and acetone, its tuneability presents opportunities for improving acetone sorption, and its ethanol sorption capacity exceeds that of similar carbon-based materials. These findings underscore GPA's capability and versatility in vapor adsorption, paving the way toward its integration into graphene-based devices for sensing applications.

Exploring the Possibility of Ionic Liquid as a Dimensional Stabilizer for Well-Preserved Waterlogged Archaeological Wood

Dehydration is the principal conservation process for waterlogged archaeological wood (WAW), with the aim of preventing shrinkage and cracking. For well-preserved WAW, shrinkage mainly takes place when the moisture content is below the fiber saturation point. Here, we conduct a new trial using ionic liquid as a dimensional stabilizer to maintain a stable swollen state of WAW. Molecular dynamics simulation (MD), shrinkage measurement, Fourier transform infrared spectroscopy (FTIR), and dynamic vapor sorption (DVS) were adopted to investigate the interactions and effects of 1-Butyl-3-methylimidazolium chloride ([Bmim][Cl]) on WAW (Dipterocarpaceae Dipterocarpus sp. with a maximum moisture content of 80.3%) in comparison with the conventional material polyethylene glycol (PEG). The results show that [Bmim][Cl] and its water mixtures have a comparable or slightly greater ability to swell amorphous cellulose than does water at room temperature, while crystalline cellulose is left intact. The samples treated with [Bmim][Cl] show less shrinkage than the PEG 300- and PEG 2000-treated samples at all tested concentrations after air-drying. The best dimension control was achieved by 40 wt% [Bmim][Cl], with volumetric shrinkage reduced from 5.03% to 0.47%. DVS analysis reveals that [Bmim][Cl] reduces moisture contents at moderate and low relative humidity (&lt;80%) when the concentration is at or below 20 wt%, which suggests that good dimensional stability was not achieved by simply preserving the moisture content but possibly through the interaction of the ionic liquid with the wood polymers.

Measurement of Sorption Isotherms to Guide Mixed Display of Archaeological Iron, Bone, and Glass.

This study examines the preservation challenges of archaeological iron, bone, and glass within shared environments focusing on material-specific degradation mechanisms. The relative humidity (RH) requirements for these materials can vary significantly. Iron presents distinct stability groups at specific RH thresholds, albeit levels below 30% RH are recommended for sensitive artefacts. Little is known about the moisture response of bone, and the heterogeneity of the material poses additional challenges for its examination. Glass can undergo deterioration at both high and low RHs due to the threat of aqueous attack and transformation of the pristine glass or the crizzling and delamination of the already transformed glass. Experiments employing dynamic vapour sorption (DVS), acoustic emission (AE), and oxygen depletion analyses provided insights into the moisture response behaviours of these materials. It was found that the deleterious akageneite formation increases dramatically at RHs > 30% in archaeological iron, reinforcing the current guidelines. Bone exhibits significant hygroscopicity as well as isotherm steepening below 25% RH on desorption, suggesting this threshold could be advisable to avoid structural damage. In glass, there is evidence of significant mass fluctuations between c. 60 and 95% RH, as well as isotherm steepening around 30% RH on desorption, thus providing more empirical evidence to published storage recommendations. This work sheds more light on the risk assessment for mixed-material showcases and underscores the necessity of nuanced RH guidelines that consider the material-specific degradation mechanisms.

Diffusion coefficient measurement using Dynamic Vapour Sorption method

Abstract Dynamic vapour sorption method (DVS) represents modern technique investigating interactions between the vapour and solid-state objects. This paper looks deeper into determination of the diffusion coefficient. The diffusion coefficient has significant importance in many technical fields and accurate data are often missing. Determination of diffusion coefficient is based on simplified theories, but real-world experiments expose their limits. Applications of dynamic vapour sorption method is demonstrated in the experiment with wooden material. It shows some pitfalls though. Further considerations for improving the accuracy and removal of errors are discussed further.

Kinetics of human insulin degradation in the solid-state: an investigation of the effects of temperature and humidity.

With the increasing development of oral peptide dosage forms, a comprehensive understanding of factors affecting peptide drug stability in the solid-state is critical. This study used human insulin, as a model peptide, to examine the individual and interactive effects of temperature and humidity on its solid-state stability. Insulin was stored at temperature (25°C, 40°C, and 6 °C) and humidity (1%, 33% and 75%) over 6 months. Primary degradation pathways were deamidation and covalent aggregation. Degradation product formation rates were determined empirically and modelled using the humidity-corrected Arrhenius equation. Temperature had a major impact on deamidation and covalent aggregation rates, with the reaction rates increasing with temperature. The effect of humidity was temperature dependent. Moisture induced degradation was minimal at 25°C and 40°C, but an important factor at 60°C. Dynamic vapour sorption analysed determined a clear differences in insulin moisture sorption characteristics at 60°C relative to 25°C and 40°C. The findings suggest that the effect of moisture on insulin deamidation and covalent aggregation rates was not a function of water content but the nature of the insulin moisture interaction.

Synthesis of fluorinated ether free aromatic backbone copolymers containing trifluoromethyl and dimethylamino groups for CO2 separation: Investigation of pure and mixed gas performance under dry and humid conditions

A novel series of linear, high molecular weight aromatic copolymers containing trifluoromethyl and dimethylamino groups was synthesized via facile super-acid catalyzed polyhydroxyalkylation and investigated as CO2 gas separation membrane materials. The molar ratio of the two ketone comonomers used in copolymerization, trifluoroacetophenone (TFAp) and N,N-dimethylamino trifluoroacetophenone (dMATFAp), was systematically varied to produce five copolymers with different dMATFAp contents ranging from 12 to 73 %. The influence of dMATFAp content on physicochemical and mechanical properties as well as pure gas and water vapor separation performance was studied. All synthesized copolymers displayed excellent film forming ability, high thermal stability and high Tg values (Tgs > 380 °C). Pure gas permeability measurements revealed that the increase of dMATFAp molar content from 12 % to 34 % resulted in improved gas permeability, while, on the contrary, further increase of dMATFAp content from 34 to 73 % led to substantial gas permeability decrease ascribed to FFV decrease. In particular, among copolymers, the one with dMATFAp content of 34 % presented the highest CO2 permeability value of 290 Barrer due to its highest CO2 diffusion and CO2 solubility coefficients associated with its higher FFV value. The CO2/CH4 performance of synthesized copolymers fell very close to 2008 upper bound limit and exceeded most of the super-acid catalyzed copolymer membranes reported in the literature and commercial membranes. CO2/CH4 and CO2/N2 selectivity values for the different synthesized copolymers were in the range of 29.9–40 and 22.7–44, respectively. The study of the effect of dMΑTFA on water permeability unveiled that the membrane with the highest dMΑTFAp molar content (73 %) showed the highest water permeability value (23,100 Barrer) as well. This was attributed to the increased concentration of N-methyl substituent of dMΑTFAp which can interact with water molecules thereby increasing solubility. Under process gas stream conditions using a mixture of 3 % H2O-48.5 % CO2-48.5 % CH4, both CH4 and CO2 permeability were significantly reduced (by 35 % and 47 %, respectively) due to the preferential sorption of water vapor over other gases present in the mixture, highlighting the negative effect of water vapor on gas permeability. Accordingly, the CO2/CH4 separation factor was slightly increased from 23.8 to 29. Finally, stability test of the copolymer (BP-TFAp)66-(BP-dMATFAp)34 at 40 °C under humid mixed gas conditions showed that CO2 and CH4 permeability remained unchanged for one month after an initial condition stabilization that is required implying that these copolymer structures are promising materials for CO2 separation.

Fluorierte Squareimine zur molekularen Trennung von aromatischen und aliphatischen Verbindungen

AbstractDie Entwicklung energieeffizienterer Trenntechnologien ist von entscheidender Bedeutung. Insbesondere die Trennung von cyclischen aliphatischen Kohlenwasserstoffen von ihren aromatischen Gegenstücken bleibt aufgrund der Bildung von Azeotropen und ähnlicher physikalischer Eigenschaften eine große Herausforderung, die oft energieintensive Prozesse erfordert. Hier stellen wir eine neue Klasse von elektronenarmen Makrocyclen mit einer einzigartigen rechteckigen Struktur vor, um Interaktionen innerhalb der Poren zu optimieren, wodurch eine hochselektive molekulare Abtrennung aromatischer Verbindungen aus diesen Mischungen ermöglicht wird. Durch die Nutzung dynamisch‐kovalenter Iminchemie wird das auf Squareimin NDI2F42‐basierende kristalline Material direkt in hoher Ausbeute (83 %) aus der Reaktionsmischung erhalten. Analog wird das größere Kongener NDI2F82 mit einer Ausbeute von 69 % gewonnen. In Dampfsorptions‐ und Diffusionsexperimenten zeigt NDI2F42 schnelle Adsorptionskinetiken mit einer Selektivität von 97 : 3 für Benzol gegenüber Cyclohexan und 93 : 7 für Toluol gegenüber Methylcyclohexan, während Röntgenstrukturanalysen an Einzelkristallen und Pulvern darauf hindeuten, dass die Selektivität hauptsächlich durch gerichtete Wechselwirkungen zwischen den elektronenarmen Paneelen und den aromatischen Gästen bestimmt wird.

Fluorinated Squareimines for Molecular Sieving of Aromatic over Aliphatic Compounds.

The development of more energy-efficient separation technologies is essential. Especially the separation of cyclic aliphatic hydrocarbons from their aromatic counterparts remains a significant challenge due to azeotrope formation and similar physical properties, often requiring energy-intensive processes. Herein, we introduce a novel class of electron-deficient macrocycles with a unique rectangular structure to optimise interactions within the pore, enabling the highly selective molecular sieving of aromatic compounds from mixtures. Utilising dynamic covalent imine chemistry, the squareimine NDI2F42-based crystalline functional material is directly obtained from the reaction mixture in a single self-assembly step in high yields of 83 %, alongside the larger NDI2F82 congener, which can be obtained in 69 % yield. In vapour sorption and diffusion experiments, NDI2F42 demonstrates rapid adsorption kinetics with selectivities of 97 : 3 for benzene over cyclohexane and 93 : 7 for toluene over methylcyclohexane, while single-crystal and powder X-ray diffraction studies indicate that the selectivity is primarily governed by directed interactions between the electron-deficient panels and aromatic guests.

Influence of Relative Humidity on the Mechanical Properties of Palm Leaf Manuscripts: Short-Term Effects and Long-Term Aging.

Palm leaf manuscripts are a valuable part of world cultural heritage. Studying the mechanical properties of palm leaf manuscripts and their changes due to environmental influences is of great significance for understanding the material characteristics, aging mechanisms, and preventive conservation of these manuscripts. This study used dynamic vapor sorption (DVS) and a thermomechanical analyzer (TMA) to investigate the changes to the mechanical properties of palm leaf manuscripts in response to different relative humidity conditions and different time periods. The short-term study results show that exposure to varying relative humidities leads to changes in the equilibrium moisture content (EMC) of palm leaf manuscripts, causing the bending strength of the samples to decrease significantly with increasing humidity. The bending modulus initially increases and then decreases as the humidity increases. Moreover, the greater the desorption hysteresis of the samples, the more pronounced the changes to the mechanical properties. Therefore, a stable environment in terms of humidity can prevent changes in the mechanical properties of palm leaf manuscripts, thereby preventing the onset of degradation. The results of the long-term aging studies indicate that prolonged exposure to either very dry or very humid conditions greatly affects the mechanical properties of palm leaf manuscripts, which is detrimental to their preservation. The samples kept at 50% RH did not exhibit significant signs of deterioration, with no notable changes in their mechanical properties or chemical structure. This suggests that 50% RH is a relatively optimal humidity condition for the preservation of palm leaf manuscripts.