Covalent organic framework membranes prepared via mixed linker modulated assembly for hydrogen peroxide enrichment

Hydrogen peroxide (H₂O₂) enrichment is a significant separation process that catches tremendous attention in energy and environment fields. Membrane technology is envisioned as a promising candidate for H₂O₂ enrichment owing to its cost-effective and environmental-friendly features. However, it is challenging to develop membrane materials tolerant to rigorous operations of H₂O₂ enrichment. Here, we explored covalent organic frameworks (COFs) as membrane materials for H₂O₂ enrichment. The all-organic and periodical assembled nature endowed COFs with excellent chemical robustness, which exhibited excellent performance for H₂O₂ enrichment. A novel mixed linker modulated assembly method was developed to modulate the interfacial polymerization for COF membrane. Hydrazine hydrate (Hz) and p-phenylenediamine (Pa) were chosen as mixed diamine linkers to synthesize the COF layer composed of TpPa and TpHz clusters. By varying the relative proportion of the mixed linkers, the pore size of COF membranes was tuned from 1.70 nm to 0.50 nm, which exhibited more pronounced size-selective ability for the separation of water and H₂O₂. Moreover, the water capture ability of membranes was also fortified by introducing hydrophilic linkers during interfacial polymerization process. As a result, the COF membranes showed a total flux of 38.35 kg m⁻² h⁻¹, H₂O/H₂O₂ separation factor of 23 and superior long-term operation performance up to 7 days, manifesting the great potential in H₂O₂ enrichment. Our study may open a novel route for engineering membranes toward molecular separations involving strong oxidative components.