Underlying Polar and Nonpolar Modification MOF-Based Factors that Influence Permanent Porosity in Porous Liquids

Improving Light-Responsive Efficiency of Type II Porous Liquid by Tailoring the Functionality of Host

Light-responsive porous liquids (LPLs) attract significant attention for their controllable gas uptake under light irradiation, while their preparation has remained a great challenge. Here we report the fabrication of type II LPLs with enhanced light-responsive efficiency by tailoring the host's functionality for the first time. The functionality of light-responsive metal-organic cage (MOC-RL, constructed from dicopper and responsive ligands) is modified by introducing the second long-chain alkyl ligand, producing MOC-RL-AL as a new host. A spatially hindered solvent based on polyethylene glycol, IL-NTf2, is designed and can dissolve MOC-RL-AL due to the suitable interaction, creating a type II LPL (PL-RL-AL). Under light irradiation, the variation in propylene adsorption for PL-RL-AL increases by 58.0 % compared to PL-RL. The enhanced light-responsive efficiency is caused by easier control in accessibility of internal cavities within MOCs and increased number of external cavities between MOCs and IL-NTf2. This makes PL-RL-AL the first LPL with the probability for propylene/propane separation.

Nonadditive CO2 Uptake of Type II Porous Liquids Based on Imine Cages

Type II porous liquids can potentially exploit the fluidity of liquids and sorption properties of porous sorbents, yet CO2 uptake in porous liquids is still poorly understood. Molecular simulations and experiments are used to examine CO2 uptake by a prototypical porous liquid composed of porous organic cages (CC13) in 2'-hydroxyacetophenone (2'-HAP). The simulations are in reasonable agreement with experimental measurements of CO2 solubility and provide unambiguous information on the partitioning of CO2 within microenvironments in the liquid. Analysis of CO2 dynamics is performed using these simulations, including assessing the self-diffusivity of CO2 in both the neat solvent and porous liquid. This offers insights into the kinetics of CO2 uptake and transport in type II porous liquids based on imine cages. Experiments with type II porous liquids formed by dissolving CC13 in three different size-excluded solvents show nonadditive CO2 absorption relative to predictions based on ideal volume additivity. This nonadditive absorption behavior is also observed in simulations. Nonadditive CO2 uptake is also demonstrated in type II porous liquids based on another imine-based porous cage, CC19.

Flexible Linker Spacer Length Modulation in Cd-Based Metal-Organic Frameworks: Impact on Polarity and Sequestration Abilities

The heightening concerns over an outbreak of hazardous radioiodine from nuclear waste and carbon dioxide emissions from fossil fuels have restricted access to clean water and air. In this work, three Cd-MOFs (1-3) are self-assembled under environment-friendly conditions using i) a polypyridyl linker spanned by a flexible poly(methylene) spacer, and ii) a bent dicarboxylate linker. With a change in the length of the flexible methylene spacer, the dimensionality of the MOFs is tuned between 3D (1) and 2D (2 and 3). The microscopic images reveal that 1 displays larger particle sizes and a more pronounced morphology compared to 2 and 3. These MOFs show high thermal stability (up to 300 °C) and wettability. A controlled polar feature of 1-3 is utilized to achieve a high uptake capacity of iodine (I2 or I3 -) from water bodies (2.46-2.37 g g-1) and vapor (3.31-2.65 g g-1). With remarkable CO2 uptake by 1-3, the sorbate CO2 is further fixated into market-value products in quantitative conversions and atom economy under room temperature and solvent-free conditions. A comprehensive theoretical support is provided by configurational biased Monte Carlo (CBMC) simulations to reveal the exact locale and binding energies of the sorbates (I2, CO2, and epoxide) toward these MOFs.

Design and Development of a Self-Supporting ZIF-62 Glass MOF Membrane with Enhanced Molecular Sieving for High H2 Separation Efficiency

The purpose of this study was to design and develop a self-supporting glass MOF membrane (GMM) including its design, fabrication under different heat treatment temperatures, analysis of its physical-chemical properties, and assessment of its separation performance. Glass MOFs preserve metal-ligand bonding structures similar to their crystalline counterparts, providing intrinsic gas separation properties alongside the benefits of amorphous materials, including reduced grain boundaries and ease of processing. In this work, ZIF-62 was melted and then cooled to fabricate GMMs using vitrification to enhance molecular sieving. This study systematically examines the impact of varying thermal treatment temperatures (400-475 °C) on the physical and chemical transformations of GMMs, revealing their effects on the porosity, defect formation, and molecular sieving performance through advanced characterization techniques (e.g., solid-state nuclear magnetic resonance (13C NMR), X-ray photoelectron spectroscopy (XPS), He pycnometry, and positron annihilation lifetime spectroscopy (PALS)). The optimal GMM exhibits an impressive separation performance, particularly for H2 separation. The GMM at 4 bar and 25 °C exhibited He, H2, CO2, N2, and CH4 gas permeations of 576.37, 509.23, 146.07, 3.45, and 2.28 barrer, respectively. The ideal selectivities of H2/CH4, CO2/N2, CO2/CH4, H2/N2, and H2/CO2 gas pairs were 223.47, 42.37, 64.10, 147.71, and 3.49, respectively, which significantly exceed earlier reported values for ZIF-62 membranes, demonstrating the significant potential for GMMs as high-performance molecular sieve membranes, particularly for H2 separation. This work by optimizing the vitrification process through systematic temperature control highlights GMM's ability to achieve high selectivity and permeability, positioning it as a promising candidate for industrial gas separation applications.

Control of Permanent Porosity in Type 3 Porous Liquids via Solvent Clustering

Porous liquids (PLs) are an exciting new class of materials for carbon capture due to their high gas adsorption capacity and ease of industrial implementation. They are composed of sorbent particles suspended in a nonadsorbed solvent, forming a liquid with permanent porosity. While PLs have a vast number of potential compositions based on the number of solvents and sorbent materials available, most of the research has been focused on the selection of the sorbent rather than the solvent. Therefore, PL design criteria on the supramolecular structures of the solvent are explored to create a fundamental understanding of how the solvent enables PL formation for rapid discovery of new PL compositions. Atomistic molecular dynamics simulation of eight solvents with a range of molecular sizes, shapes, and intramolecular bonding was performed, identifying that the shape and size of molecular clusters formed in the solvent are the driving predictor of PL formation rather than the size of the individual solvent molecule. The results demonstrate a significant departure from common approaches to PL formation based on the steric exclusion of solvent molecules from the sorbent via the size of the pore aperture. A modeling and experimental validation study further supports these findings. Through this computational material design study, a previously unexplored mechanism in PL formation, solvent-solvent clustering, is identified as a critical factor for the accelerated discovery of liquid phase carbon capture materials.

Thermodynamic Evidence for Type II Porous Liquids

Porous liquids are an emerging class of microporous materials where intrinsic, stable porosity is imbued in a liquid material. Many porous liquids are prepared by dispersing porous solids in bulky solvents; these can be contrasted by the method of dissolving microporous molecules. We highlight the latter "Type II" porous liquids-which are stable thermodynamic solutions with demonstrable colligative properties. This feature significantly impacts the ultimate utility of the liquid for various end-use applications. We also describe a facile method for determining if a Type II porous liquid candidate is "porous" based on assessing the partial molar volume of the porous host molecule dissolved in the solvent by measuring the densities of candidate solutions. Conventional CO₂ isotherms confirm the porosity of the porous liquids and corroborate the facile density method.

Recent Advances in Catalytic Pyrolysis of Municipal Plastic Waste for the Production of Hydrocarbon Fuels

Currently, the resources of fossil fuels, such as crude oil, natural gas, and coal, are depleting day by day due to increasing energy demands. Nowadays, plastic items have witnessed a substantial surge in manufacturing due to their wide range of applications and low cost. Therefore, the amount of plastic waste is increasing rapidly. Hence, the proper management of plastic wastes for sustainable technologies is the need of the hour. Chemical recycling technologies based on pyrolysis are emerging as the best waste management approaches due to their robustness and better economics. However, research on converting plastic waste into fuels and other value-added goods has yet to be undertaken, and more R&D is required to make waste-plastic-based fuels economically viable. In this review article, the current status of the plastic waste pyrolysis process is discussed in detail. Process-controlling parameters such as temperature, pressure, residence time, reactor type, and catalyst dose are also investigated in this review paper. In addition, the application of reaction products is also described in brief. For example, plasto-oil obtained by catalytic pyrolysis may be utilized in various sectors, e.g., transportation, industrial boilers, and power generation. On the other hand, byproducts, such as solid residue (plasto-char), could be used as a road construction material or to make activated carbon or graphenes, while the non-condensable gases have a good potential to be utilized as heating/energy source.