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Nickel-based pore-space-partitioned (PSP) metal-organic frameworks (MOFs) offer modular pore environments and superior adsorption capacities; however, some of them exhibit extreme susceptibility to humidity resulting in the facile reduction of trivalent metal ions and structural distortion. Here, we report a sequential growth-etching-recycling process that chemically and structurally stabilizes moisture-sensitive PSP MOFs by transforming them into robust hollow architectures. Upon the introduction of Ga3+ and 1,4-benzenedicarboxylic acid to a moisture-unstable Ni-CPM-33a template, template-induced epitaxial growth of a moisture-stable PSP MOF shell occurs at the exterior. Simultaneously, metal ion-driven internal etching of the template facilitates the recycling of dissolved chemicals, yielding hollow GaNi-CPM-33a while preserving the partitioned acs topology. Detailed structural and chemical analyses verify that the resulting compositions align with a stepwise exterior-growth/interior-etching/component-recycling mechanism. Hollow GaNi-CPM-33a demonstrates excellent stability under ambient humidity, maintaining high crystallinity and porosity, whereas the original Ni-CPM-33a undergoes rapid structural distortion. This enhanced moisture stability together with its advantageous hollow architecture improves the adsorption performance for toxic chemicals, such as chemical warfare agent simulants, under ambient humidity, exceeding the capacity of Ni-CPM-33a by over 30-fold. This strategy also effectively constructs an isoreticular Ni-CPM-33d system containing different linkers. Furthermore, the well-defined cavity of these hollow PSP MOFs enables efficient encapsulation of Au nanoparticles to form rattle-like Au@GaNi-CPM-33a via the growth of Ni-CPM-33a on Au surface followed by the growth-etching-recycling process. This study establishes a versatile and convenient route to synthesize moisture-stable hollow PSP MOFs for toxic vapor adsorption under ambient humidity and functional nanoconfinement.
Choi et al. (Fri,) studied this question.