Two-Dimensional Covalent Organic Framework Solid Solutions

Rebecca L. Li, Anna Yang, Nathan C. Flanders, Michael T. Yeung, Daylan T. Sheppard, William R. Dichtel*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Scopus citations


Covalent organic frameworks (COFs) generally leverage one or two monomers with specific sizes and shapes to access highly symmetric and periodic polymer networks. Almost all reported COFs employ the minimum sets of monomers needed for the polymerization (usually two, sometimes one) and crystallize in high-symmetry topologies. COFs synthesized from more than two monomers usually employ mixtures with different pendant functionalities to distribute these groups statistically throughout the structure, or monomers with different sizes in ratios targeting lower symmetry topologies. Here, we demonstrate that mixtures of monomers with different lengths generate single-phase, hexagonal two-dimensional covalent organic framework (2D COF) solid solutions at continuously variable feed ratios. X-ray diffraction measurements, Fourier-transform infrared spectroscopy, and Pawley refinement indicate that both monomers distribute randomly within the same lattice, and the lattice parameters continuously increase as more of the larger linker is incorporated. Furthermore, COF solid solutions are accessed directly by polymerizing a mixture of monomers but not via linker exchange from a preformed COF. As strain develops from the lattice accommodating monomers with different sizes, the nonlinear relationship between the monomer incorporation and the COF's lattice parameters suggests that bond-bending of the monomers plays a role in incorporating monomers of different lengths into the solid solutions. Solid solution formation represents a new strategy to design 2D COFs and increase their complexity. Specifically, varying the monomer composition of a given network enables many properties, such as the average pore size, to be continuously tuned between those of corresponding pure COFs.

Original languageEnglish (US)
Pages (from-to)7081-7087
Number of pages7
JournalJournal of the American Chemical Society
Issue number18
StatePublished - May 12 2021

ASJC Scopus subject areas

  • Catalysis
  • Chemistry(all)
  • Biochemistry
  • Colloid and Surface Chemistry


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