Zr-MOF with free carboxylic acid for storage and controlled release of caffeine

Zr-based metal-organic-frameworks (MOFs) such as UiO-66 and UiO-66-COOH were prepared and applied for storage and delivery of caffeine (CAF) in order to understand the possible application of the MOFs in CAF delivery and chemical interactions that are crucial for the delivery. Compared with conventional activated carbon, both UiO-66s showed much higher (at least by ~60%) adsorptions of CAF. By introduction the functional group (-COOH) on the UiO-66, the release rate was decreased noticeably. More importantly, the delivery rate could be adjusted by changing the solution pH. The observed delivery rates from CAF@UiO-66-COOH could be explained with H-bonding. Therefore, it could be suggested that MOFs are very attractive in drug storage/delivery especially when functional groups onto the MOFs can interact selectively with drugs.