Abstract
Controlling the two-dimensional polymerization processes of two-dimensional covalent organic frameworks (2D COFs) is essential to fully realizing their distinct properties. Although most 2D COFs have been isolated as polycrystalline aggregates with only nanometer-scale crystalline domains, we have identified rapid, solvothermal conditions that provide micrometer-scale and larger single-crystal 2D polymers for a few 2D COFs. Yet it remains unclear why certain conditions produce far larger 2D polymers than others, which hinders generalizing these findings. The guiding principles for controlled two-dimensional polymerization in solution remain unclear. Here, we study the crystallization processes of both single-crystalline and polycrystalline 2D COFs using ultrasmall-angle X-ray scattering (USAXS) for the first time, through which we characterized COF formation conditions with scattering data collected every few seconds. In situ USAXS experiments revealed distinct growth mechanisms between single-crystalline and polycrystalline COFs and suggested a nonclassical particle fusion-based growth model for single-crystalline COFs that results in faceted, hexagonal particles. These findings were corroborated by in situ wide-angle X-ray scattering (WAXS) experiments and scanning electron microscopy (SEM). In contrast, polymerizations that provide polycrystalline COFs evolve as spherical aggregates that do not fuse in the same way. These insights into how micrometer-sized, crystalline 2D polymers are formed in solution point a way forward to establishing a robust connection between the 2D polymer structure and designed properties by controlling their polymerization processes.
Original language | English (US) |
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Pages (from-to) | 16775-16786 |
Number of pages | 12 |
Journal | Journal of the American Chemical Society |
Volume | 146 |
Issue number | 24 |
DOIs | |
State | Published - Jun 19 2024 |
Funding
We acknowledge the Army Research Office (ARO) for supporting this research under Grant Number (W911NF-23-1-0306). We acknowledge the European Synchrotron Radiation Facility (ESRF) for the provision of synchrotron radiation facilities, and we would like to thank Dr. Theyencheri Narayanan and Dr. Gouranga Manna for assistance and support in using beamline ID02 under proposal CH-6646. We thank Dr. Jan Ilavsky at the APS for providing guidance on best practices for modeling and reporting the USAXS data. This work benefited from the use of the SasView application, originally developed under NSF Award DMR-0520547. SasView also contains code developed with funding from the EU Horizon 2020 programme under the SINE2020 project Grant Number 654000. In situ WAXS experiments were performed at the DuPont-Northwestern-Dow Collaborative Access Team (DND-CAT) located at Sector 5 of the Advanced Photon Source (APS). DND-CAT is supported by Northwestern University, The Dow Chemical Company, and DuPont de Nemours, Inc. 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. Data were collected using an instrument funded by the National Science Foundation under Award Number 0960140. We would like to acknowledge Dr. Steven Weigand for facilitating our experiments at the APS. We also thank Dr. Michael Traxler, Dr. Xavier Aguilar-Enriquez, and Zoheb Hirani for their assistance in performing initial experiments at the APS. This work has made use of the Integrated Molecular and Structure Education and Research Center (IMSERC) at Northwestern University, which has received support from the National Science Foundation (NSF) through Grant Number (CHE-1048773). This work has also made use of the Electron Probe Instrumentation Center (EPIC) and Keck II facilities of the Northwestern University Atomic and Nanoscale Characterization Experiment (NUANCE) Center, which has received support from the Soft and Hybrid Nanotechnology Experimental (SHyNE) Resource (NSF; ECCS-1542205), the MRSEC program (NSF; DMR-1720139) at the Materials Research Center, the Keck Foundation, the State of Illinois, and the International Institute for Nanotechnology (IIN). A.N. was supported by the Ryan Fellowship and IIN. I.R.L. acknowledges the Swiss National Science Foundation (SNSF) Postdoc Mobility Grant Number (P500PN_206836).
ASJC Scopus subject areas
- Catalysis
- General Chemistry
- Biochemistry
- Colloid and Surface Chemistry