Covalent organic frameworks (COFs)—highly porous, sponge-like materials built from organic (carbon-based) molecules connected by strong chemical bonds—could offer a new route to longer-lasting fragrance delivery, with researchers demonstrating how pore chemistry can be engineered to control both fragrance loading and release rates. The approach could give formulators a more precise way to tailor fragrance longevity based on the polarity and molecular characteristics of individual ingredients.
In a study published in Food Chemistry*, researchers developed three imine-based COFs—TAPB-DHTP-COF, TAPB-DMTP-COF and TAPB-DVA-COF—using a solvent-evaporation method. The materials featured adjustable surface areas of 152–1,056 m²/g and pore sizes of 2.3–3.9 nm, providing different environments for capturing and retaining volatile fragrance molecules.
Testing with three fragrance ingredients revealed a clear relationship between molecular polarity and encapsulation performance. The polar aldehydes anisaldehyde and citral showed substantially stronger adsorption than the nonpolar terpene limonene. Density functional theory (DFT) calculations attributed the difference to hydrogen bonding, with adsorption energies of -1.16 eV for anisaldehyde and -1.17 eV for citral, compared with just -0.37 eV for limonene.
The researchers also demonstrated sustained fragrance release over 48 hours from all fragrance-loaded COFs, compared with rapid release from the unencapsulated ingredients. Release rates could be adjusted by changing the strength of host-guest interactions: stronger hydrogen bonding produced more prolonged release.
Effectively, carrier chemistry could be matched to the molecular properties of individual fragrance ingredients to achieve specific loading and release profiles. This could support longer-lasting performance in cosmetics and personal care, while potentially improving fragrance stability and reducing rapid evaporation.
The COFs also offer a potential alternative to metal-organic frameworks (MOFs), which have been investigated for fragrance delivery but can contain metals such as zirconium, cobalt and chromium. Because COFs are built from covalently bonded organic components, the researchers describe their platform as heavy-metal-free, chemically stable and structurally tunable.
The work remains an early materials-development demonstration rather than a validated commercial delivery system. Further evaluation of sensory performance, carrier safety, biodegradability, formulation compatibility and manufacturing economics will be important in determining its practical potential.
*Authors were affiliated with the school of Flavour Fragrance and Cosmetics, Shanghai Institute of Technology, School of Medical Science and Engineering, Beijing Institute of Technology, and School of Pharmaceutical Sciences, Guangzhou Medical University, Guangzhou.
