Rational design and synthesis of a novel ternary metal–organic framework with a (3,5)-connected topology for iodine capture

The discovery of metal-organic frameworks (MOFs) with novel structures opens significant opportunities to improve their performance in gas storage, separation, and catalysis. Rational design of building blocks plays a pivotal role in the construction of new MOF architectures. In this work, we demonstrate that temperature control is an effective strategy for directing the formation of geometrically distinct secondary building units (SBUs), thereby enabling the synthesis of a novel framework. Specifically, lowering the reaction temperature from 105 °C to 75 °C promotes the formation of Zn₂ SBUs over the thermodynamically favored Zn₄O SBUs, resulting in the assembly of a new (3,5)-connected framework, CCNUF-7, instead of the previously reported ternary (3,6)-connected SC-MOF-2. Due to the rare trigonal bipyramidal geometry of the Zn₂ SBUs, CCNUF-7 adopts an unprecedented topological net featuring zigzag hexagonal channels with a diameter of ∼18.5 Å. Furthermore, CCNUF-7 exhibits a high iodine uptake capacity of 2.89 g g^-1, attributed to its high porosity and abundant binding sites. This work highlights the potential of temperature-controlled SBU engineering as a powerful approach for constructing MOFs with unprecedented topologies.