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A simple approach was developed to computationally construct a polymer dataset by combining simplified molecular-input line-entry system (SMILES) strings of a targeted polymer backbone and a variety of molecular fragments. This method was used to create 14 polymer datasets by combining seven polymer backbones and molecules from two large molecular datasets (MOSES and QM9). Polymer backbones that were studied include four polydimethylsiloxane (PDMS) based backbones, poly(ethylene oxide) (PEO), poly(allyl glycidyl ether) (PAGE), and polyphosphazene (PPZ). The generated polymer datasets can be used for various cheminformatics tasks, including high-throughput screening for gas permeability and selectivity. This study utilized machine learning (ML) models to screen the polymers for CO 2 /CH 4 and CO 2 /N 2 gas separation using membranes. Several polymers of interest were identified. The results highlight that employing an ML model fitted to polymer selectivities leads to higher accuracy in predicting polymer selectivity compared to using the ratio of predicted permeabilities.

A computational scheme was used to screen physical solvents for CO 2 pre-combustion capture by integrating the commercial NIST database, an in-house computational database, chem-informatics, and molecular modeling. A commercially available screened hydrophobic solvent, diethyl sebacate, was identified from the screening with favorable physical properties and promising absorption performance. The promising performance to use diethyl sebacate in CO 2 pre-combustion capture has also been confirmed from experiments. Water loading in diethyl sebacate is very low, and therefore, water is kept with H 2 in the gas stream. The favorable CO 2 interaction with diethyl sebacate and the intermediate solvent free volume fraction leads to both high CO 2 solubility and high CO 2 /H 2 solubility selectivity in diethyl sebacate. An in-house NETL computational database was built to characterize CO 2 , H 2 , N 2 , and H 2 O interactions with 202 different chemical functional groups. It was found that 13% of the functional groups belong to the strong interaction category with the CO 2 interaction energy between -15 and -21 kJ/mol; 62% of the functional groups interact intermediately with CO 2 (-8 to -15 kJ/mol). The remaining 25% of functional groups interact weakly with CO 2 (below -8 kJ/mol). In addition, calculations show that CO 2 interactions with the functional groups are stronger than N 2 and H 2 interactions but are weaker than H 2 O interactions. The CO 2 and H 2 O interactions with the same functional groups exhibit a very strong linear positive correlation coefficient of 0.92. The relationship between CO 2 and H 2 gas solubilities and solvent fractional free volume (FFV) has been systematically studied for seven solvents at 298.2 K. A skewed bell-shaped relation was obtained between CO 2 solubility and solvent FFV. When an organic compound has a density approximately 10% lower than its density at 298.2 K and 1 bar, it exhibits the highest CO 2 loading at that specific solvent density and FFV. Note that the solvent densities were varied using simulations, which are difficult to be obtained from the experiment. In contrast, H 2 solubility results exhibit an almost perfect positive linear correlation with the solvent FFV. The theoretical maximum and minimum physical CO 2 solubilities in any organic compound at 298.2 K were estimated to be 11 and 0.4 mol/MPa L, respectively. An examination of 182 experimental CO 2 physical solubility data and 29 simulated CO 2 physical solubilities shows that all the CO 2 physical solubility data are within the maximum and minimum with only a few exceptions. Finally, simulations suggest that in order to develop physical solvents with both high CO 2 solubility and high CO 2 /H 2 solubility selectivity, the solvents should contain functional groups which are available to interact strongly with CO 2 while minimizing FFV.

Nanoporous silica membranes exhibit excellent H 2 /CO 2 separation properties for sustainable H 2 production and CO 2 capture but are prepared via complicated thermal processes above 400 °C, which prevent their scalable production at a low cost. Here, we demonstrate the rapid fabrication (within 2 min) of ultrathin silica-like membranes (∼3 nm) via an oxygen plasma treatment of polydimethylsiloxane-based thin-film composite membranes at 20 °C. The resulting organosilica membranes unexpectedly exhibit H 2 permeance of 280-930 GPU (1 GPU = 3.347 × 10 -10 mol m -2 s -1 Pa -1 ) and H 2 /CO 2 selectivity of 93-32 at 200 °C, far surpassing state-of-the-art membranes and Robeson's upper bound for H 2 /CO 2 separation. When challenged with a 3 d simulated syngas test containing water vapor at 200 °C and a 340 d stability test, the membrane shows durable separation performance and excellent hydrothermal stability. The robust H 2 /CO 2 separation properties coupled with excellent scalability demonstrate the great potential of these organosilica membranes for economic H 2 production with minimal carbon emissions.

An effective cross-linking technique allows a viscous and highly gas-permeable hydrophilic polyphosphazene to be cast as solid membrane films. By judicious blending with other polyphosphazenes to improve the mechanical properties, a membrane exhibiting the highest CO 2 permeability (610 barrer) among polyphosphazenes combined with a good CO 2 /N 2 selectivity (35) was synthesized and described here. The material demonstrates performance stability after 500 h of exposure to a coal-fired power plant flue gas, making it attractive for use in carbon capture applications. Its CO 2 /N 2 selectivity under conditions up to full humidity is also stable, and although the gas permeability does decline, the performance is fully recovered upon drying. The high molecular weight of these heteropolymers also allows them to be cast as a thin selective layer on an asymmetric porous membrane, yielding a CO 2 permeance of 1200 GPU and a CO 2 /N 2 pure gas selectivity of 31, which does not decline over 2000 h. In addition to gas separation membranes, this cross-linked polyphosphazene can potentially be extended to other applications, such as drug delivery or proton exchange membranes, which take advantage of the polyphosphazene's versatile chemistry.

Metal-organic framework (MOF) nanosheets are attracting more and more attention due to their tunable porous structure and two-dimensional shape. Adding MOF nanosheets into polymers can lead to improved properties, but the level of enhancement is usually thwarted by the difficulties in exfoliating and aligning these nanosheets within the polymer matrix. In order to establish a strategy for making polymer/MOF nanosheets composites with improved exfoliation and alignment, we combined MOF nanosheets and polymer using layer-by-layer (LbL) assembly for the first time. MOF nanosheets (ZIF67-L, leaf-like zeolitic imidazolate framework nanosheets) used in this study were functionalized with positively charged polyethylenimine, which could replace the original surface ligands and impart a positive charge on the nanosheet surface. These positively charged MOF nanosheets were then combined with negatively charged poly(acrylic acid) through ionic-bonding-assisted LbL assembly, generating a polymer composite with fully exfoliated and highly aligned MOF nanosheets.

Metal organic framework (MOF)/polymer composite membranes are of interest for gas separations, as they often have performance that exceeds the neat polymer. However, traditional composite membranes, known as mixed matrix membranes (MMMs), can have complex and time-consuming preparation procedures. The MOF and polymer are traditionally prepared separately and require priming and mixing to ensure uniform distribution of particles and compatibility of the polymer-particle interface. In this study, we reduce the number of steps using an in situ MOF growth strategy. Herein, MMMs are prepared by growing MOF (UiO-66) in situ within a Matrimid polymer matrix while simultaneously curing the matrix. The gas separation performance for MMMs, prepared using this approach, was evaluated for the CO 2 /N 2 separation and compared with MMMs made using the traditional postsynthesis mixing. It was found that MMMs prepared using both the in situ MOF growth strategy and by traditional postsynthesis mixing are equivalent in performance. However, using the in situ MOF growth allows for a simpler, faster, and potentially more economical fabrication alternative for MMMs.

We have utilized an environmentally friendly synthesis approach for the accelerated growth of a selective inorganic membrane on a polymeric hollow fiber support for postcombustion carbon capture. Specifically, continuous defect-free ZIF-8 thin films were grown and anchored using continuous flow synthesis on the outer surface of porous supports using water as solvent. These membranes demonstrated CO 2 permeance of 22 GPU and the highest reported CO 2 /N 2 selectivity of 52 for a continuous flow synthesized ZIF-8 membrane.