Nature Communications, Published online: 07 August 2026; doi:10.1038/s41467-026-76345-2 Covalent organic frameworks (COFs) emerged as promising candidates for singlet oxygen generation, yet their structure-property-activity relationships remain poorly understood. Here the authors construct three constitutionally isomeric donor-acceptor COFs which involves precise modulation of the imine and pyridine nitrogen positions within the skeleton.