Retrievable ultrafast covalent triazine framework membranes for organic solvent nanofiltration

Covalent organic frameworks (COF) membranes are considered as promising candidates for organic solvent nanofiltration (OSN) due to their well-defined porosity, high perm-selectivity, and exceptional resistance to solvents. However, irreversible membrane fouling caused by filter cake layers or pore clogging challenges the robust separation over long-term operation especially for well-known COF membranes. Here, we present novel ultrafast covalent triazine frameworks (CTF) membranes with retrievable separation performances for OSN processes. CTF-1 membrane with unitary nanopore and CTF-m membrane with binary nanopore are fabricated via an air-organic solvent interfacial polymerization technique for comparison, which demonstrates molecular-level selectivity (MWCO, ∼320 Da for CTF-1 and ∼ 625 Da for CTF-m) and ultrafast permeability for polar organic solvents. Moreover, the heterogeneous skeleton nanopores structure of CTF-m membranes facilitates efficient separation of photogenerated carriers, thus resulting in retrievable permselectivity. This work offers an efficient strategy via Donor-Acceptor structure modulation to tackle OSN membrane fouling, paving the way for applications of framework membranes.