Exploring the Isoreticular Continuum between Phosphonate- and Phosphinate-Based Metal–Organic Frameworks

The rational design of metal–organic frameworks (MOFs) is one of the driving forces behind the great success that this class of materials is experiencing. The so-called isoreticular approach is a key design tool, very often used to tune the size, steric properties, and additional functional groups of the linker used. In this work, we go one step further and show that even linkers with two different coordinating groups, namely, phosphonate and phosphinate, can form isoreticular MOFs. This effectively bridges the gap between MOFs utilizing phosphinate and phosphonate coordinating groups. Using a novel bifunctional ligand, 4-[hydroxy(methyl)phosphoryl]phenylphosphonic acid [H3PPP(Me)], we were able to prepare ICR-12, a MOF isoreticular to already published MOFs containing bisphosphinate linkers (e.g., ICR-4). An isostructural MOF ICR-13 was also successfully prepared using 1,4-benzenediphosphonic acid. We envisage that this strategy can be used to further enlarge the pool of MOFs.金属有机框架（metal–organic frameworks, MOFs）的理性设计，是该类材料当前取得巨大成功的核心驱动力之一。所谓等网状合成法（isoreticular approach）是关键的设计策略，常被用于调控桥连配体的尺寸、空间位阻特性与额外官能团。本研究在此基础上更进一步，证实即便带有膦酸基团（phosphonate）与次膦酸基团（phosphinate）这两种不同配位基团的桥连配体，也可构筑等网状MOFs。该成果有效填补了采用次膦酸配位基团与膦酸配位基团的MOFs之间的研究空白。借助新型双功能配体4-[羟基(甲基)膦酰基]苯基膦酸[H3PPP(Me)]，我们成功制备出ICR-12，该MOF与已发表的含双次膦酸桥连配体的MOFs（如ICR-4）具有等网状结构。利用1,4-苯二膦酸，我们还成功制备出同构MOF ICR-13。我们预期该策略可用于进一步拓展MOFs的材料体系。