摘要
Exploring new linkage chemistry is of fundamental significance for covalent organic frameworks(COFs)to expand their structure and functional diversity.Herein,we report a strategy for converting azine linkage into urea-and thiourea-based fused-ring connections in COFs by criss-cross[3+2]dipolar cycloaddition of azine with HNCO or KSCN.The as-prepared COFs with cyclized linkages exhibited enhanced chemical and thermal stability by locking the dynamic C=N linkages in the progenitor.Moreover,functions could be introduced into the skeleton of COFs by this postsynthetic cyclization method,which enabled significant improvements in functionality,demonstrated by the studies on CO_(2)/N_(2) selective sorption,proton conduction,and Hg^(2+)adsorption.The use of this[3+2]cycloaddition strategy not only enriched the chemistry of linkage conversion for COFs but also offered a new way to fabricate fused-ring-linked COFs,thereby representing a high level of controllability on connectivity and functionality of COFs.
基金
supported by the National Science Fund for Distinguished Young Scholars of China(grant no.21725404)
the Science and Technology Committee of Shanghai Municipality,China(grant no.20JC1415400).
