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For the sake of water and energy conservation, development of latent heat cooling and thermal storage systems that minimize water consumption and operate with higher efficacy than their water-driven counterparts is a crucial task. Phase change materials (PCMs) present a potential solution, but their integration into real-world systems abounds with scientific challenges such as material toxicity, flammability, low thermal performance and lack of tunable phase-change temperatures. In this study we report on a first-in-class nanocomposite PCM that leverages non-flammable, non-toxic, high latent heat sugar alcohols (SAs) encapsulated within easy-to-synthesize zeolitic imidazolate framework (ZIF) crystals. We also outline a practical route for surface functionalization with hydrophilic and hydrophobic moieties. The SA@ZIF composites display suppressed phase-change temperatures which, together with alterable surface functionality, broadens their applicability to a plethora of working environments. Direct synthesis of the SA@ZIF composite generates nanoconfined SAs with phase-change temperatures as low as 19.8 °C and latent heats as high as 285 J g-1. This nanoconfinement-induced thermal phenomenon is conserved even after functionalization of the SA@ZIF crystal surface. We believe this study will lay the groundwork as a platform for next generation high performing, tunable PCMs to aid in the realization of waterless cooling systems.

Membrane-based separations can mitigate the capital- and energy-intensive challenges associated with traditional thermally driven processes. To further push the boundary of gas separations, mixed matrix membranes (MMMs) have been extensively exploited; however, identifying an optimal nanofiller to boost the separation performance of MMMs beyond Robeson permeability-selectivity upper bounds remains an ongoing challenge. Here, a new class of MMMs based on pyrazine-fused crystalline porous graphitic frameworks (PGFs) is reported. At a loading of 6 wt % PGFs, the MMMs surpass the current H2/CH4 Robeson upper bound, ideally suited for applications such as H2 regeneration. In addition, the fabricated MMMs exhibit appealing CO2 separation performance, closely approaching the current Robeson upper bounds for CO2 separation. Compared with the pristine polymeric membranes, the PGF-based MMMs display a record-high enhancement of gas permeability over 120% while maintaining intrinsic gas selectivities. Highlighting the crucial role of the crystallinity of nanofillers, this study demonstrates a facile and effective approach in formulating high-performance MMMs, complementing state-of-the-art membrane formation processes. The design principles open the door to energy-efficient separations of gas mixtures with enhanced productivity compatible with the current membrane manufacturing.

Membrane separation technology provides substantial savings in energy and cost for molecular separations in chemical industry, ideally complementing conventional thermally driven separation approaches. However, current membranes are subject to limitations, primarily lying in the Robeson permeability-selectivity upper bound limits. In this study, hydroxy metal-organic framework (MOF)/polyimide mixed-matrix membranes are found to enable high separation performance for applications including CO2 capture and hydrogen purification while offering enhanced compatibility with state-of-the-art membrane-manufacturing processes. The mixed-matrix membranes exceed the present Robeson upper bounds with H2 and CO2 permeabilities of 907 and 650 Barrers, respectively and H2 /CH4 and CO2 /CH4 selectivities of 45 and 32, respectively. The unparalleled performance results from intimate interactions at the boundary of the hydroxy MOFs and carboxylic polymers through strong hydrogen bonds. The principle of design opens the door to highly permeable membranes with synergistic compatibility with established membrane manufacturing platforms for energy-efficient molecular separations.

Forward osmosis (FO) has emerged as a new technology for desalination and exhibits potentials for applications where reverse osmosis is incapable or uneconomical for treating streams with high salinity or fouling propensity. However, most of current draw agents in FO are salts and difficult to be recycled cost- and energy-effectively. In this work, we demonstrate a new and facile approach to efficiently recover water from the FO process with enhanced water purity by using a binary ion liquid/hydrogel system. The hybrid ion liquid/hydrogel draw solution system demonstrated in this work synergistically leverages the thermoresponsive properties of both the ionic liquid (IL) and hydrogel to improve the overall FO performance. Our findings corroborate that the hydrogel mitigates the water flux decline of the IL as the draw agent and provide a ready route to contiguously and effectively regenerate water from the FO process. Such a route allows for an efficient recovery of water from the draw solute/water mixture with enhanced water purity, compared with conventional thermal treating of lower critical solution temperature IL draw solute/water. Furthermore, hydrogels can be used in a continuous and readily recyclable process to recover water without heating the entire draw solute/water mixture. Our design principles open the door to use low-grade/waste heat or solar energy to regenerate draw agents and potentially reduce energy in the FO process considerably.

Polymer‐based membrane technology holds immense promise for CO2 separation. However, it faces persistent challenges, including the high CO2 pressure‐induced plasticization and permeability‐selectivity trade‐offs, which significantly hinder the development of polymeric membranes. To tackle this issue, we synthesized a novel polyimide 6FDA‐DAT:DABA(6FDD) containing triptycene and carboxylic groups. Upon de‐carboxylation induced cross‐linking, the membrane demonstrated a simultaneous enhancement of gas permeability and selectivity. Specifically, compared to the uncross‐linked 6FDD, the 400°C‐24 h cross‐linked membrane exhibited a remarkable increase in CO2 permeability by 177% (93.1 Barrer) and a significant rise in CO2/CH4 selectivity by 47% (57.5), reaching the CO2/CH4 upper bound. More importantly, the cross‐linked membrane displayed vastly improved CO2 plasticization resistance, withstanding up to 42 bar of CO2 feed pressure. The design of decarboxylated cross‐linked membranes in this work paves the way for creating high‐performing and plasticization‐resistant membranes with potential applications in high‐pressure CO2 separations. [ABSTRACT FROM AUTHOR]

Membrane separation technology provides substantial savings in energy and cost for molecular separations in chemical industry, ideally complementing conventional thermally driven separation approaches. However, current membranes are subject to limitations, primarily lying in the Robeson permeability–selectivity upper bound limits. In this study, hydroxy metal‐organic framework (MOF)/polyimide mixed‐matrix membranes are found to enable high separation performance for applications including CO2 capture and hydrogen purification while offering enhanced compatibility with state‐of‐the‐art membrane‐manufacturing processes. The mixed‐matrix membranes exceed the present Robeson upper bounds with H2 and CO2 permeabilities of 907 and 650 Barrers, respectively and H2/CH4 and CO2/CH4 selectivities of 45 and 32, respectively. The unparalleled performance results from intimate interactions at the boundary of the hydroxy MOFs and carboxylic polymers through strong hydrogen bonds. The principle of design opens the door to highly permeable membranes with synergistic compatibility with established membrane manufacturing platforms for energy‐efficient molecular separations. [ABSTRACT FROM AUTHOR]

Abstract: High-performance ester-crosslinked hollow fiber membranes were evaluated for sensitivity to aggressive hydrocarbon and water impurities. The hollow fiber samples show improved separation productivity and hydrocarbon-induced antiplasticization resistance under extremely challenging feed conditions in comparison to previously reported cases. The CO2 permeance was improved from 10GPU to 50GPU with a CO2/CH4 selectivity of 28 in testing at an 800psi 50/50 CO2/CH4 feed with 1000ppm (molar) toluene, 35°C. Moreover, membrane samples with different skin layer thicknesses show significantly different sensitivities to toluene. The thinner skinned samples are hypothesized to have higher fractional free volume (FFV) and hence show more tendency to antiplasticize when exposed to impurities as compared to thicker skinned samples. The high separation performance of crosslinked hollow fibers was fully recovered after removing the high-level contaminants, including toluene and heptane, and showed negligible changes over 100h exposure to a 600psi 50/50 CO2/CH4 feed with 750ppm toluene, indicating a strong stability against contaminants. Furthermore, exposure to 101ppm (molar) water impurity did not cause an apparent subsequent change in the separation properties. The excellent properties in the presence of hydrocarbon and water contaminants demonstrate that ester-crosslinked hollow fiber membranes are attractive for natural gas purification, even under more aggressive operating conditions. [Copyright &y& Elsevier]

High-performance ester-cross-linkablecomposite hollow fibers were developed through simultaneous spinningof 4,4′-(hexafluoroisopropylidene) diphthalic anhydride (6FDA)based polyimide and Torlon (registered trademark of Solvay Polymers)solutions. The core layer polyamide-imide polymer, Torlon, demonstratesexcellent adhesion with cross-linkable 6FDA-based polyimide duringspinning and ester-cross-linking. Torlon also shows superior thermalstability after cross-linking while maintaining the open substructureof the Torlon core layer. The resultant cross-linked composite hollowfibers show a CO2permeance of 40 GPU with a CO2/CH4selectivity of 39 in testing at 100 psi with 50/50CO2/CH4feed, 35 °C. The cross-linked compositehollow fibers also show high separation performance in the presenceof high-level toluene contaminants up to 1000 ppm, suggesting thatcross-linked composite hollow fibers are viable under realistic operationconditions. The high natural gas separation performance and significantlyreduced cost of hollow fiber formation provides a significant advancementin the state of the art for natural gas separations. [ABSTRACT FROM AUTHOR]