2D-MATERIALS VIA ORGANIC SYNTHESIS
Recent News: Our materials team of Hoberg, Parkinson, de Sousa Oliveira and Brant received an NSF DMREF GOALI award for "Salt Separation Membranes Based on Modifiable 2D Covalent Organic Frameworks."
COF SYNTHESIS
The Hoberg group focuses on the design, synthesis and characterization of 2D Covalent Organic Frameworks (COFs) in collaboration with Professor Bruce Parkinson. COFs are honeycomb like structures that are constructed from small building blocks via covalent linkages to produce highly ordered, porous structures. As illustrated below, the condensation of amines with ketones lead to polymeric COFs in which we tune the pores via synthetic modifications. We construct membranes with these materials to perform a variety of applications that include separations.
APPLICATIONS
Below is one example of a COF designed to filter at a specific size (published in JACS). Using a COF that incorporates 12 carboxylate groups per pore, a highly negatively charged pore is produced. This was evaluated for cation selectivity in membranes by fabrication onto a track-etched polycarbonate membrane support (TEPC). Using a potentiostat, ion transport was measured by recording current-voltage curves. The slope of the linear current-voltage (I-V) curves was used to define the resistance of the membrane indicative of the ability to support an ion current across it. The figure reveals that TEPC membranes with large 200 nm diameter pores facilitate ion transport pathways for all the cations. As seen, the COF/TEPC membranes possess excellent ion selectivity towards the ammonium cations of various sizes. The higher cation conductivity of the smaller cations, including NH4, Me4N, Et4N, Bu4N and Hex4N, indicates that these cations can pass through the COF/TEPC membrane, due to their smaller size (Hex4N radius = 8.2 Å) than the COF pores (radius = 13.5 Å). As noticed, the decreasing conductivity trend from NH4+to Hex4N+for COF/TEPC is similar to that of bare TEPC membrane due to their smaller transference numbers. The significant drop in conductivity of COF/TEPC membranes for the larger cations (Oct4N radius = 10.9 Å and dodecyl = 15.1 Å) reveals the nearly complete rejection of larger cations by the COF layer, demonstrating its high cation size selectivity.
Applications to the separations of proteins such as BSA and globulin have also been studied. Water permeance as high as 1000 (L/m2h1bar1) and 99% protein rejection have been achieved. This can be compared to commercial membranes where water permeance of only 100-200 is achieved.
THE GROUP
A collaborative research effort comprised of synthetic organic chemists, chemical engineers and materials scientists.
Current members: Michael Wenzel (PhD student), Kira Kirkham (PhD student), Dr. Bhausaheb Kashinath Dhokale (post doc), Emma Muller, Isaac Lass, Cailin Brugger.
Former members: Dr. Phuoc Duong, Dr. Valerie Kuehl, Veronica Spaulding, Rylie Pilon, Emily Fretland, Carlyn Cook.
Collaborators Prof. John Brant, Laura de Sousa Oliveira & Bruce Parkinson
COF PUBLICATIONS
Recent COF publications
"Mechanistic study of pH effect on organic solvent nanofiltration using carboxylated covalent organic framework as a modeling and experimental platform" Duong, P. H. H.; Shin, Y. K.; Kuehl, V. A.; Afroz, M. M.; Hoberg, J. O.; Parkinson, B. A.; van Duin, A. C. T.; Li-Oakey, K. D.Separation and Purification Technology 2022, 282, 120028.
"Synthesis, post-synthetic modifications and applications of the first Quinoxaline-based Covalent Organic Framework" Kuehl, V. A.; Duong, P. H. H.; Sadrieva, D.; Amin, S. A.; She, Y.; Li-Oakey, K. D.; Larger, J. L.; Parkinson, B. A.; Hoberg, J. O.* ACS Appl. Mater. Interfaces 2021, 13, 37494-37499.
https://doi.org/10.1021/acsami.1c08854
"Pitfalls in the Synthesis of Polyimide-linked Two-dimensional Covalent Organic Frameworks" Kuehl, V. A.; Wenzel, M. J.; Oliveira, L. S.; Parkinson, B. A.; Hoberg, J. O.* J. Mat. Chem. A 2021, 9, 15301-15309.
https://doi.org/10.1039/d1ta01954f
“A self-assembling, biporous, metal-binding covalent organic framework and its application for gas separation” Spaulding, V.; Zosel, K.; Duong, P. H. H.; Li-Oakey, K. D.; Parkinson, B. A.; Gomez-Gualdron, D. A.; and Hoberg, J. O.* Mater. Adv. 2021, 2, 3362-3369.
https://doi.org/10.1039/d1ma00056j
"The influence of disorder in the synthesis, characterization and applications of a modifiable two-dimensional Covalent Organic Framework" Brophy, J.; Summerfield, K.; Yin, J.; Kephart, J.; Stecher, J.T.; Adams, J.; Yanase, T.; Brant, J.; Li-Oakey, K. D.; Hoberg, J. O.*; Parkinson, B. A.* Materials 2021, 14, 71.
https://doi.org/10.3390/ma14010071
"Molecular Interactions and Layer Stacking Dictate Covalent Organic Framework Effective Pore Size" Duong, P. H. H.; Kuehl, V. A.; Shin, Y. K.; Hoberg, J.; Parkinson, B. A.; van Duin, A. C.; Li-Oakey, K. D.O.* ACS Appl. Mater. Interfaces 2021, 13,
doi.org/10.1021/acsami.1c10866.
“Carboxyl-functionalized covalent organic framework as a two-dimensional nanofiller for mixed-matrix ultrafiltration membranes” Duong, P. H. H.; Kuehl, V. A.; Mastorovich, B.; Hoberg, J. O.; Parkinson, B. A.; Li-Oakey, K. D.* J. Membr. Sci. 2019,574, 338-348.
https://doi.org/10.1016/j.memsci.2018.12.042
“A highly-ordered nanoporous, two-dimensional covalent organic framework with modifiable pores, and its application in water purification and ion sieving.” Kuehl, V. A.; Yin, J.; Duong, P. H. H.; Mastorovich, B.; Newell, B.; Li-Oakey, K. D.; Parkinson, B. A.*; Hoberg, J. O.* J. Am. Chem. Soc. 2018,140, 18200-18207.
https://doi.org/10.1021/jacs.8b11482
“Hydrogen gas formation from the photolysis of rhenium hydrides - mechanistic and computational studies” Webster, A.; Huo, J.; Milliken, J.; Sullivan, P.; Kubelka, J.; Hoberg, J. O.* Dalton Tran. 2019, 48, 16148-16152.
https://doi.org/10.1039/c9dt03364e