Salicylideneanilines-Based Covalent Organic Frameworks as Chemoselective Molecular Sieves.

Porous materials such as covalent organic frameworks (COFs) are good candidates for molecular sieves due to the chemical diversity of their building blocks, which allows fine-tuning of their chemical and physical properties by design. Tailored synthesis of inherently functional building blocks can generate framework materials with chemoresponsivity, leading to controllable functionalities such as switchable sorption and separation. Herein, we demonstrate a chemoselective, salicylideneanilines-based COF (SA-COF), which undergoes solvent-triggered tautomeric switching. This is unique compared to solid-state salicylideneanilines' counterpart, which typically requires high energy input such as photo or thermal activation to trigger the enol-keto tautomerisim and cis-trans isomerization. Accompanying the tautomerization, the ionic properties of the COF can be tuned reversibly, thus forming the basis of size-exclusion, selective ionic binding or chemoseparation in SA-COF demonstrated in this work.