Understanding fragility and engineering activation stability in two-dimensional covalent organic frameworks

Abstract

The sensitivity of covalent organic frameworks (COFs) to pore collapse during activation processes is generally termed activation stability. Activation stability is important for achieving and maintaining COF crystallinity and porosity,...

Construction of symbiotic one-dimensional ionic channels in a cobalt-based covalent organic framework for high-performance oxygen reduction electrocatalysis

“…Bu et al 49 restored the crystallinity of the COF by treatment with different polar solvents. Zhu et al 50 quantified the activity and crystallinity of the COF, which is very enlightening and may further be used to improve the catalytic performance of the materials.…”

Solvent-Induced Incremental Pore Collapse in Two-Dimensional Covalent Organic Frameworks

“…We note that we only tested moderate temperatures, and higher temperatures which produce significant lattice expansion can lead to structure changes and loss of crystallinity. 22,23 Next, we tested whether the presence of residual high surface tension solvent could impact COF crystallinity and porosity. To test this, we synthesized Py-2P COF and washed it in the high surface tension solvent THF.…”

“…14 Activation stability is also related to the COF properties and molecular structure. For example, a prior report by some of us 23 elucidated the relationship between pore collapse and COF chemistry, structures, and architectures. COFs with smaller pore sizes and larger substituents tend to be more stable and show higher activation stability than those with larger pore sizes and smaller-sized substituents.…”

“…These results demonstrate that the temperature used during activation is relatively unimportant compared to the activation solvent surface tension. We note that we only tested moderate temperatures, and higher temperatures which produce significant lattice expansion can lead to structure changes and loss of crystallinity. , …”

Crystallinity of Imide-Linked Two-Dimensional Polymers Depends on the Nucleophilicity of Triamine Building Blocks

“…Based on this concept, the study of 2DPs has focused on reversible reactions, such as boronic acid and catechol condensation, imine condensation, hydrazone formation, Knoevenagel condensation, and so on . The reversible reaction allows for an understanding of mechanistic insights for the bond formation of 2DP. − Furthermore, challenges for preserving the crystallinity and porosity of 2DPs with fragile and/or flexible building blocks have been amply discussed. − Apart from these linkages, imide-linked 2DPs (PI-2DPs) have been investigated, because of their good physicochemical stability and good mechanical properties. , These intrinsic properties allow them to expand their applications as energy-related, adsorbent, and separation materials. − However, the development of PI-2DPs has lagged behind the aforementioned formations of reversible covalent linkages, for two reasons . First, anhydride groups, which have one of two monomers (triamine + dianhydride) for PI-2DPs, are mostly restricted by two-fold (C 2 ) symmetry, thereby limiting the available number of PI-2DPs.…”