Polymer-Coated Covalent Organic Frameworks as Porous Liquids for Gas Storage

Rachel E Mow; Glory A Russell-Parks; Grace E B Redwine; Brittney E Petel; Thomas Gennett; Wade A Braunecker

doi:10.1021/acs.chemmater.3c02828

Polymer-Coated Covalent Organic Frameworks as Porous Liquids for Gas Storage

Chem Mater. 2024 Jan 19;36(3):1579-1590. doi: 10.1021/acs.chemmater.3c02828. eCollection 2024 Feb 13.

Authors

Rachel E Mow^{1

2}, Glory A Russell-Parks^{3

2}, Grace E B Redwine^{3

2}, Brittney E Petel⁴, Thomas Gennett^{1

3

2}, Wade A Braunecker^{3

2}

Affiliations

¹ Materials Science Program, Colorado School of Mines, Golden, Colorado 80401, United States.
² Chemistry and Nanoscience Center, National Renewable Energy Laboratory, 15013 Denver West Pkwy, Golden, Colorado 80401, United States.
³ Department of Chemistry, Colorado School of Mines, 1012 14th Street, Golden, Colorado 80401, United States.
⁴ Catalytic Carbon Transformation and Scale-Up Center, National Renewable Energy Laboratory, 15013 Denver West Pkwy, Golden, Colorado 80401, United States.

Abstract

Several synthetic methods have recently emerged to develop high-surface-area solid-state organic framework-based materials into free-flowing liquids with permanent porosity. The fluidity of these porous liquid (PL) materials provides them with advantages in certain storage and transport processes. However, most framework-based materials necessitate the use of cryogenic temperatures to store weakly bound gases such as H₂, temperatures where PLs lose their fluidity. Covalent organic framework (COF)-based PLs that could reversibly form stable complexes with H₂ near ambient temperatures would represent a promising development for gas storage and transport applications. We report here the development, characterization, and evaluation of a material with these remarkable characteristics based on Cu(I)-loaded COF colloids. Our synthetic strategy required tailoring conditions for growing robust coatings of poly(dimethylsiloxane)-methacrylate (PDMS-MA) around COF colloids using atom transfer radical polymerization (ATRP). We demonstrate exquisite control over the coating thickness on the colloidal COF, quantified by transmission electron microscopy and dynamic light scattering. The coated COF material was then suspended in a liquid polymer matrix to make a PL. CO₂ isotherms confirmed that the coating preserved the general porosity of the COF in the free-flowing liquid, while CO sorption measurements using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) confirmed the preservation of Cu(I) coordination sites. We then evaluated the gas sorption phenomenon in the Cu(I)-COF-based PLs using DRIFTS and temperature-programmed desorption measurements. In addition to confirming that H₂ transport is possible at or near mild refrigeration temperatures with these materials, our observations indicate that H₂ diffusion is significantly influenced by the glass-transition temperature of both the coating and the liquid matrix. The latter result underscores an additional potential advantage of PLs in tailoring gas diffusion and storage temperatures through the coating composition.