scheme1

Scheme 1. Historical development of acetylenic polymers. (A) Previously reported acetylenic polymers and corresponding structures; (B) This study presents the synthesis of 2D COFs and the proposed mechanism of transforming them into crystalline CL-COFs via solid-state cross-linking in confined spaces. COFs: Covalent organic frameworks; CL-COFs: crystalline cross-linked covalent organic frameworks.