N-Heterocyclic Organobase-Mediated Interfacial Polymerization for the Rapid Synthesis of Highly Crystalline COF Membranes

Covalent organic frameworks (COFs) are ideal candidates for constructing high-performance molecular separation membranes. Interfacial polymerization (IP) represents an important approach for fabricating continuous COF membranes. This study presents an N-heterocyclic organobase-mediated IP (N-het-IP) strategy to rapidly fabricate highly crystalline, continuous COF membranes at the interface. The key of the N-het-IP strategy lies in the presynthesized aqueous-phase tertiary amine intermediates derived from the N-heterocyclic organobase (such as piperazine) and aldehyde monomers (such as Tp). The tertiary amine intermediates with a Tp core and N-heterocyclic segments take part in the dynamic amine exchange reaction with organic-phase amine monomers, inducing interfacial membrane formation and COF crystalline transformation within 30 min under mild conditions. Simultaneously, the interfacial assembly of the tertiary amine intermediates constructs an amphiphilic interfacial microenvironment, regulating self-arrangement and suppressing disordered stacking, thereby yielding highly crystalline, continuous, and defect-free COF membranes. Moreover, the N-het-IP strategy exhibits broad universality, being compatible with various N-heterocyclic organobases and amine monomers of diverse COF membranes. Constructed via the N-het-IP strategy, the resulting COF membrane exhibits moderately high permeance and enables precise molecular sieving of dyes. The N-het-IP strategy provides a facile and efficient method to synergize the rapid synthesis and continuous assembly of COF membranes, paving the way for the development of COF membranes tailored for on-demand molecular separations.