Dynamic Pore Space Partition in Zinc Metal–Organic Frameworks

Increasing the framework connectivity is a useful strategy to tune pore geometry and properties such as gas separation selectivity. Although highly connected frameworks are common for iconic clusters such as M₃(O/OH) trimers and Zr₆(O/OH)₈ hexamers, they are rarely seen for Zn₄O tetramers, one of the most famed MOF building blocks that predates both M₃ and Zr₆ in the MOF field. Here, we demonstrate that pore space partition (PSP) can unlock the potential of Zn₄O for higher connectivity (>6). We show that on the pore-space-partitioned acs (pacs) platform, zinc-cluster chemistry is diverse and dynamic, yet it can be mapped out semiquantitatively. A large family of Zn_x-pacs materials (x = 2, 3, 4) with 3 different pore-partition mechanisms has been synthesized by applying PSP to the MOF-5-type system. We propose that the difference in the steric effect around 9-connected Zn₃(OH) and Zn₄O, exacerbated when the hexagonal c/a ratio is compressed, plays a key role in the discovery of a new pacs family based on 9-connected Zn₄O. This work significantly broadens the scope of PSP because it no longer requires preoriented open-metal sites. New pacs materials show much better aqueous stability and greatly enhanced C₂H₂/C₂H₄ separation performance than the corresponding nonpartitioned MOF-5-type materials.