Figure 1.

Several reversible reactions used for construction of COF materials. Dynamic reversible reactions are essential for the formation of crystal covalent organic frameworks (COFs). These reversible reactions for the formation of COFs are boron-containing linkages (for example, boroxine, boronate ester, borazine and spirobrate), nitrogen-containing linkages (for example, imine, hydrazone, azine, squaraine, phenazine, triazine, imide and azodioxy), and a double-stage linkage containing the boronate ester linkage and the imine linkage in one COF via a one-pot reaction.