Straightforward construction of hollow polyoxometalate-based metal-organic framework via pseudo-homoepitaxial growth

Hollow structures are significant for shortening diffusion path and promoting active center exposure. Single-crystalline hollow polyoxometalate-based metal-organic frameworks (POM@MOFs) with increased adsorption performance and catalytic activity were synthesized through a straightforward pseudo-homoepitaxial growth strategy within only 1.5 min. The strategy ingeniously exploits favorable characteristics of well-matched lattice/structure but acid stability difference between MOF and POM@MOF to construct a pseudo-homoepitaxial structure. Specifically, the MOF single crystals are used as seeds to perform epitaxial growth of the lattice/structure-matched POM@MOF under appropriate conditions. Interestingly, the MOF seeds collapse spontaneously during epitaxial growth, affording regular hollow POM@MOF single crystals. Because the acid stability of the POM@MOF is much higher than that of the MOF, it is speculated that the hollow structure formation may be related to the acid released from the epitaxial POM@MOF growth. And the pseudo-homoepitaxial POM@MOF growth strategy based on structural matching but stability difference avoids additional template removal process in conventional hollow MOF preparation and ensures hollow single crystal construction.