Metal-organic networks, including metal-organic frameworks and metal-organic cage-based supramolecular frameworks, possess high specific surface area and tunable pore structures, showing significant potential in gas adsorption and separation. However, under conditions of high humidity, acidity, or alkalinity, their structures are prone to degradation, leading to pore collapse and performance loss, which severely limits their practical application in complex industrial environments.
The combination of metal-organic networks with polymers to form composites has emerged as a promising strategy to tackle this issue. One common method is internal void polymerization, where polymer chains grow within the internal cavities. However, this process often leads to the blockage of pores, dramatically reducing pore size and surface area. To overcome this limitation, researchers have developed an alternative approach: the introduction of polymers on the surface of metal-organic networks via surface polymerization.
For instance, Liu and coworkers enhanced the mechanical stability of MSF-1 by surface polymerization of hexamethylene diisocyanate, obtaining MSF-1@PolyHDI. Yang and coworkers used surface polymerization of isophorone diisocyanate to stabilize photo-responsive PCC-20t, yielding PCC-20t@PolyIDI. Li and coworkers enhanced the moisture resistance of fragile MOF-5 by constructing a hydrophobic covalent organic framework shell, NTU-COF, to yield MOF-5@NTU-COF.
The diverse polymers introduced through surface polymerization bring multiple advantages. First, mechanical and chemical stability can be enhanced without compromising porosity. During polymerization, formed polymer chains inhibit monomer mass transfer, promoting surface-coated polymer formation. MSF-1@PolyHDI displayed improved framework stability with BET surface area increased from 561 to 2600 m²·g⁻¹, while PCC-20t@PolyIDI exhibited an 18.6-fold increase in BET surface area compared to activated PCC-20t. Importantly, the pore size distribution of these composites remained consistent with their pristine structures. Similarly, this approach maintained the pore structure of MOF-5 and enabled complete CO₂/N₂ separation under humid conditions.
Beyond stability, this strategy also enhances performance. MSF-1@PolyHDI showed methane adsorption capacity up to 186 cm³·g⁻¹ at 56 bar, compared to only about 62 cm³·g⁻¹ for MSF-1 at the same pressure. Notably, PCC-20t@PolyIDI exhibited a 27.9% change in CO₂ adsorption capacity under visible and ultraviolet light irradiation, significantly higher than the 7.0% change observed in activated PCC-20t, demonstrating improved regulation efficiency.
The surface polymerization strategy offers comprehensive advantages and represents an effective pathway toward next-generation high-performance composite materials. Looking forward, researchers propose constructing functionally synergistic composite architectures by designing polymer layers as molecular sieves while metal-organic networks provide high-capacity adsorption sites, potentially overcoming the traditional trade-off between adsorption capacity and selectivity. Additionally, functional polymers incorporating stimuli-responsive groups could enable external control of properties, expanding adsorptive separation applications. These research directions rest squarely on the decisive advantage that surface polymerization leaves the internal pore architecture unperturbed—a benefit that further amplifies the merits of this strategy.

DOI
10.1007/s11705-026-269-7