Transformation of a Hydrazone-Linked Covalent Organic Framework into a Highly Stable Hydrazide-Linked One

The development of covalent organic frameworks (COFs) with advanced linkages and exceptional chemical stability is of importance but remains a challenge. Herein, a hydrazone-linked COF (hydrazone-MTH-TFPB COF) was converted through mild oxidation into a hydrazide-linked one (hydrazide-MTH-TFPB COF). The hydrazide-linked COF exhibited high crystallinity, permanent porosity, and superb chemical stability in boiling water, strong acid, and strong base conditions. Moreover, hydrazide-MTH-TFPB COF displayed superior iodine uptake relative to hydrazone-MTH-TFPB COF, presumably due to the favorable interaction between iodine molecules and hydrazide moieties in the oxidized COF. This work delineates a facile approach for accessing hydrazide-linked COFs that are otherwise difficult to crystallize de novo.