Publications by authors named "Albert X Wu"

3 Publications

  • Page 1 of 1

Leveraging Free Volume Manipulation to Improve the Membrane Separation Performance of Amine-Functionalized PIM-1.

Angew Chem Int Ed Engl 2021 Mar 12;60(12):6593-6599. Epub 2021 Feb 12.

Department of Chemical Engineering, Massachusetts Institute of Technology, 77 Massachusetts Ave, Cambridge, MA, 02139, USA.

Gas-separation polymer membranes display a characteristic permeability-selectivity trade-off that has limited their industrial use. The most comprehensive approach to improving performance is to devise strategies that simultaneously increase fractional free volume, narrow free volume distribution, and enhance sorption selectivity, but generalizable methods for such approaches are exceedingly rare. Here, we present an in situ crosslinking and solid-state deprotection method to access previously inaccessible sorption and diffusion characteristics in amine-functionalized polymers of intrinsic microporosity. Free volume element (FVE) size can be increased while preserving a narrow FVE distribution, enabling below-upper bound polymers to surpass the H /N , H /CH , and O /N upper bounds and improving CO -based selectivities by 200 %. This approach can transform polymers into chemical analogues with improved performance, thereby overcoming traditional permeability-selectivity trade-offs.
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http://dx.doi.org/10.1002/anie.202012441DOI Listing
March 2021

MOF-Based Membranes for Gas Separations.

Chem Rev 2020 Aug 1;120(16):8161-8266. Epub 2020 Jul 1.

Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.

Metal-organic frameworks (MOFs) represent the largest known class of porous crystalline materials ever synthesized. Their narrow pore windows and nearly unlimited structural and chemical features have made these materials of significant interest for membrane-based gas separations. In this comprehensive review, we discuss opportunities and challenges related to the formation of pure MOF films and mixed-matrix membranes (MMMs). Common and emerging separation applications are identified, and membrane transport theory for MOFs is described and contextualized relative to the governing principles that describe transport in polymers. Additionally, cross-cutting research opportunities using advanced metrologies and computational techniques are reviewed. To quantify membrane performance, we introduce a simple membrane performance score that has been tabulated for all of the literature data compiled in this review. These data are reported on upper bound plots, revealing classes of MOF materials that consistently demonstrate promising separation performance. Recommendations are provided with the intent of identifying the most promising materials and directions for the field in terms of fundamental science and eventual deployment of MOF materials for commercial membrane-based gas separations.
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http://dx.doi.org/10.1021/acs.chemrev.0c00119DOI Listing
August 2020

Mixed-Matrix Membranes Formed from Imide-Functionalized UiO-66-NH for Improved Interfacial Compatibility.

ACS Appl Mater Interfaces 2019 Aug 14;11(34):31257-31269. Epub 2019 Aug 14.

Department of Chemical Engineering , Massachusetts Institute of Technology , Cambridge , Massachusetts 02139 , United States.

Mixed-matrix membranes (MMMs) formed by dispersing metal-organic framework (MOF) particles in polymers have attracted significant attention because these composite systems can potentially surpass the separation performance of pure polymers alone. However, performance improvements are often unrealized because of poor interfacial compatibility between the MOF and the polymer, which results in interfacial defects. From a practical perspective, strategies are needed to address these defects so that MMMs can be deployed in real-world separation processes. From a fundamental perspective, strategies are needed to reliably form defect-free MMMs so that transport models can be applied to estimate pure MOF property sets, thereby enabling the development of robust structure-property relationships. To address these interfacial challenges, we have developed a method to surface-functionalize a UiO-66-NH MOF with a nanoscopic shell of covalently tethered 4,4'-(hexafluoroisopropylidene)diphthalic anhydride-Durene oligomers. When combined with a high-molecular-weight polymer of identical chemical structure to that of the imide-functional MOF surface, defect-free MMMs with uniform particle dispersions can be formed. With this technique, both permeabilities and selectivities of select gases in the MMMs were improved at loadings ranging from 5 to 40 wt %. At a 40 wt % loading, CO permeability and CO/CH selectivity were enhanced by 48 and 15%, respectively. Additionally, pure MOF permeabilities for H, N, O, CH, and CO were predicted by the Maxwell model.
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http://dx.doi.org/10.1021/acsami.9b07500DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6727620PMC
August 2019