Interfacing and Growth Pathways of Metal-Organic Frameworks with Morphological Evolution

Hybrid metal-organic frameworks (MOFs) that integrate multiple components or structures via MOF-on-MOF growth offer promising avenues for constructing highly valued MOFs. However, understanding and controlling the anisotropic MOF-on-MOF growth that occurs between MOFs with mismatched lattices remain challenging, particularly when designing hybrid MOFs that integrate highly mismatched structures. In this study, interfacing and growth behaviors of MOFs during anisotropic MOF-on-MOF processes were demonstrated and governed by the degree of lattice matching between the constituent frameworks. For In-MIL-53C, anisotropic growth along its {110} plane, a favored exposure surface, occurs on the exposed {010} facets of the In-MIL-68B template, where a 19.5% lattice mismatch remains adjustable for MOF-on-MOF growth. In contrast, In-MIL-53D exhibits a substantial mismatch (41.2%) with the template along its {110} plane, which is too large to accommodate MOF-on-MOF. Instead, the growth proceeds via its {010} plane (a typically unfavored surface to be exposed), because it offers ideal lattice matching (only a 1.0% mismatch) with the template. The morphological features of the grown In-MIL-53s, along with their structural analyses, support their differentiated interfacial growth behaviors, demonstrating that unfavorable and unstable MOF surfaces can be selected as an interface for the MOF-on-MOF, considering their structural compatibility. Moreover, monitoring the reaction reveals the sequence of seeding, merging, and growth during the MOF-on-MOF assembly. Three sequential MOF-on-MOF growths produce a complex hybrid, In-MIL-68B@In-MIL-53C@In-MIL-68B-Br@In-MIL-53C, with five well-defined segments, including an H-shaped empty space. This series of growth comprises selective, dominant, or minimal growth, depending on the exposed template surface, along with concurrent template etching.