Dual-ActionNO Delivery from One Mixed Metal Metal–OrganicFramework

Owing to their varied and controllable reticular chemistry, metal–organic frameworks (MOFs) represent excellent, structurally precise material platforms for creating multifunctional devices. This flexibility allows the design of MOFs to feature two different delivery mechanisms for the medicinal gas nitric oxide (NO) within one structure: a rapid, kinetic release of preadsorbed NO and subsequent continuous, catalytic generation of NO on exposure to a suitable substrate. In our approach, this was realized by preparing mixed metal MOF-74 analogues (also known as CPO-27) combining two metals, namely, nickel and copper. The introduction of 10 atom % nickel into Cu-MOF-74 provides a material platform with a number of excellent properties: (i) a high capacity of NO can be released with a moisture-triggered mechanism; (ii) the available copper sites allow the (potentially indefinite) catalytic generation of NO in the presence of S-nitrosoglutathione (GSNO), a store of NO in the human body; and (iii) it features prolonged material stability on exposure to phosphates. This material therefore shows great promise as part of the next generation of multifunctional MOF-based medicinal devices.