Isovalent Heterometallic Pore-Space-Partitioned Metal-Organic Frameworks

Metal trimers are versatile MOF building units, and heterometallic trimers can enable the modulation of charge, stability, and catalytic properties. While heterometallic trimers are known in other MOFs, the pacs (partitioned acs) platform has an extraordinary capacity to access unprecedented compositions due to its high isoreticular tolerance toward component variations. Currently, heterometallic combinations on pacs are largely limited to charge-complementary systems (2+/3+). In comparison, isovalent (2+/2+) and mixed isovalent-heterovalent (2+/2+/3+) combinations have been little studied. These underexplored compositions can be significant, as divalent metals with different ionic radii and redox properties can enable property control without changing the framework charge. Here, ten new pacs were synthesized from Co, Ni, V, Fe, and In using two framework-forming ligands (L1) and four pore-partitioning linkers (L2), affording frameworks that incorporate either 2+/2+ or 2+/2+/3+ trimers, including unprecedented compositions such as CoNiV and CoNiIn. Uniform incorporation of different metal ions within the same crystals was confirmed by EDS mapping. These new materials exhibit functional versatility, combining high C₂H₂/CO₂ separation selectivity (23.8 at 298 K, 1 bar) with electrocatalytic OER activity. Compositional variations in trimers significantly influence catalytic behavior, underscoring the potential of heterometallic trimers as a platform for structural and functional tuning in MOFs.