Hetero-interpenetrated metal–organic frameworks

Interpenetrated metal–organic frameworks (MOFs) comprise two or more lattices that are mutually entangled. Interpenetration can be used to tune the structures and pore architectures of MOFs to influence, for example, their stability or interactions with guest molecules. The interpenetrating sublattices are typically identical, but hetero-interpenetrated MOFs, which consist of sublattices that are different from one another, have also been serendipitously produced. Here we describe a strategy for the deliberate synthesis of hetero-interpenetrated MOFs. We use the cubic α-MUF-9 framework as a host sublattice to template the growth of a second sublattice within its pores. Three different secondary sublattices are grown—two of which are not known as standalone MOFs—leading to three different hetero-interpenetrated MOFs. This strategy may serve to combine different properties into one material. We produce an asymmetric catalysis by allocating separate roles to the interpenetrating sublattices in a hetero-interpenetrated MOF: an achiral secondary amine on one sublattice provides the catalytic activity, while the chiral α-MUF-10 host imparts asymmetry to aldol and Henry reactions. Interpenetration—in which two or more lattices are catenated—is common in metal–organic frameworks (MOFs). Now a deliberate synthesis of hetero-interpenetrated MOFs, with two distinct lattices, has been developed. It can combine the different properties of the two sublattices in one material, as demonstrated with chirality and catalytic activity, delivering an asymmetric catalyst.