Facile stabilization of a cyclodextrin metal-organic framework under humid environment via hydrogen sulfide treatment

Increasing resistance to humid environments is a major challenge for the application of γ-CD-K-MOF (a green MOF) in real-world utilisation. γ-CD-K-MOF-H₂S with enhanced moisture tolerance was obtained by simply treating MOF with H₂S gas. XPS, Raman and TGA characterizations indicated that the H₂S molecules coordinated with the metal centers in the framework. H₂S acting as a newly available water adsorption potential well near the potassium centers protects the metal-ligand coordination bond from attack by water molecules and thus improves the moisture stability of MOF. After 7 days exposure in 60% relative humidity, γ-CD-K-MOF-H₂S retained its crystal structure and morphology, while γ-CD-K-MOF had nearly collapsed. In addition, the formaldehyde uptake tests indicated that γ-CD-K-MOF retain their permanent porosity after interaction with H₂S. This simple and facile one-step strategy would open a new avenue for preparation of moisture stable MOFs for practical applications.