A Macrocycle-Based Supramolecular Strategy for Interchangeable Screwdriver-Like on-Demand Post-Functionalization of Covalent Organic Framework.

Constructing functionalized covalent organic frameworks (COFs) through post-functionalization constitutes one of the most important approaches to applications, but is frequently plagued by limited reaction types, tedious synthesis of different precursors, and time-consuming screening of synthetic parameters for COFs. Moreover, their functions are difficult to change once the functionalities are covalently attached to COF skeletons. Herein, we report a macrocycle-based supramolecular strategy for variable noncovalent post-functionalization on the same COF platform like an interchangeable screwdriver. As a proof of concept, pillar[5]arene (P5A) with electron-rich cavity is incorporated into COF as macrocycle host to anchor different electron-deficient guests of various functions. Such a design allows tunable post-functionalization of COF through host-guest interactions for customized utilities, which has been demonstrated by using a series of guests including organic salts for iodine capture and cyano-based ligands for metal ion separation. Removing the guests enables recycling of COF, consecutive reinstallation of different guests, and continuous use for implementing expected tasks. This work establishes a general noncovalent approach to on-demand interchangeable post-functionalization of COFs.