Abstract
Two-dimensional covalent organic frameworks (2D COFs) are periodic, permanently porous, and lightweight solids that are polymerized from topologically designed monomers. The predictable design and structural modularity of these materials make them promising candidates for applications including catalysis, environmental remediation, chemical separations, and organic electronics, many of which will require stability to mechanical and thermal stress. Based on their reinforced structures and high degradation temperatures, as determined by thermal gravimetric analysis (TGA), many reports have claimed that COFs have excellent thermal stability. However, their stability to heat and pressure has not been probed using methods that report on structural changes rather than the loss of volatile compounds. Here, we explore two structurally analogous 2D COFs with different polymerization chemistries using in operando X-ray diffraction (XRD), which demonstrates the loss of crystallinity at lower temperatures than the degradation temperatures measured by TGA. Density functional theory calculations suggest that an asymmetric buckling of the COF lattice is responsible for the observed loss of crystallinity. In addition to their thermal stability, XRD of the 2D COFs under gas pressures up to 100 bar showed no loss in crystallinity or structural changes, indicating that these materials are robust to mechanical stress by applied pressure. We expect that these results will encourage further exploration of COF stability as a function of framework design and isolated form, which will guide the design of frameworks that withstand demanding application-relevant conditions.
| Original language | English |
|---|---|
| Pages (from-to) | 9883-9887 |
| Number of pages | 5 |
| Journal | Industrial and Engineering Chemistry Research |
| Volume | 58 |
| Issue number | 23 |
| DOIs | |
| State | Published - Jun 12 2019 |
Funding
We acknowledge the Army Research Office for a Multidisciplinary University Research Initiative (MURI) award, under Grant No. W911NF-15-1-0447. A.M.E. is supported by the NSF Graduate Research Fellowship (under Grant No. DGE- 1324585), the Ryan Fellowship, and the Northwestern University International Institute for Nanotechnology (IIN). This study made use of the IMSERC and EPIC at Northwestern University both of which have received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (Nos. NSF NNCI-1542205 and NSF ECCS1542205 respectively), the State of Illinois, and the IIN. M.R.R. acknowledges the U.S. Department of Energy Office of Science (Basic Energy Sciences) for research funding and the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility, operated under Contract No. DE-AC02-05CH11231, for access to supercomputing resources. N.C.F. and L.X.C. are partially supported by Basic Energy Science, CBG Division, U.S. Department of Energy through Argonne National Laboratory under Contract No. DE-AC02-06CH11357. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory, under Contract No. DE-AC02-06CH11357. We would also like to acknowledge Andrey Yakovenko of Beamline 17-BM-B for assistance with experimental setup and helpful discussions. This contribution was identified by Session Chair Amit Naskar (Oak Ridge National Laboratory) as the Best Presentation in the New Synthesis and Characterization of Polymers session of the 2018 ACS Spring National Meeting in New Orleans. We acknowledge the Army Research Office for a Multidisciplinary University Research Initiative (MURI) award, under Grant No. W911NF-15-1-0447. A.M.E. is supported by the NSF Graduate Research Fellowship (under Grant No. DGE-1324585), the Ryan Fellowship, and the Northwestern University International Institute for Nanotechnology (IIN). This study made use of the IMSERC and EPIC at Northwestern University, both of which have received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (Nos. NSF NNCI-1542205 and NSF ECCS1542205, respectively), the State of Illinois, and the IIN. M.R.R. acknowledges the U.S. Department of Energy Office of Science (Basic Energy Sciences) for research funding and the National Energy Research Scientific Computing Center (NERSC), a U.S. Department of Energy Office of Science User Facility, operated under Contract No. DE-AC02-05CH11231, for access to supercomputing resources. N.C.F. and L.X.C. are partially supported by Basic Energy Science, CBG Division, U.S. Department of Energy through Argonne National Laboratory under Contract No. DE-AC02-06CH11357. This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory, under Contract No. DE-AC02-06CH11357. We would also like to acknowledge Andrey Yakovenko of Beamline 17-BM-B for assistance with experimental setup and helpful discussions. This contribution was identified by Session Chair Amit Naskar (Oak Ridge National Laboratory) as the Best Presentation in the New Synthesis and Characterization of Polymers session of the 2018 ACS Spring National Meeting in New Orleans. *E-mail: [email protected]. ORCID Austin M. Evans: 0000-0002-3597-2454 Matthew R. Ryder: 0000-0002-1363-8148 Edon Vitaku: 0000-0002-0057-4245 William R. Dichtel: 0000-0002-3635-6119 Notes This manuscript has been coauthored by UT-Battelle, LLC under Contract No. DE-AC05-00OR22725 with the U.S. Department of Energy. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a nonexclusive, paid-up, irrevocable, worldwide license to publish or reproduce the published form of this manuscript, or allow others to do so, for United States Government purposes. The Department of Energy will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan (http://energy.gov/ downloads/doe-public-access-plan). The authors declare no competing financial interest.