A design strategy based on geometric analysis of linker shape and flexibility is developed in the context of achieving predictable topology of tetratopic-linker based Zr microporous coordination polymers (MCPs). Tetratopic linkers are categorized into tetrahedral, planar square, or planar rectangular groups based on symmetry with an emphasis on linker flexibility. A prediction framework solely based on linker shape and cluster connectivity derived from this strategy is applied to all 18 reported tetratopic-linker based Zr MCPs, and their determined topologies fit well into the scheme. Two new Zr MCPs (UMCM-312 and UMCM-313) are produced using designed linkers based on the strategy to test the robustness of prediction. UMCM-312 contains a biphenyl-core based tetratopic linker to target tetrahedral shape, and UMCM-313 takes advantage of a perylene based tetratopic linker to achieve rectangular shape. The experimentally determined topologies confirm predictions. It is thus demonstrated that the uncertainty of targeting topologies in tetratopic-linker based Zr MCPs can be reduced by accounting for linker shape and flexibility.

Ligands with flexible conformations add to the structural diversity of metal–organic frameworks but, at the same time, pose a challenge to structural design and prediction. Representative examples include Zr-tetracarboxylate-based MOFs, which afford assorted structures for a wide range of applications, but also complicate the structural control. Herein, we systematically studied the formation mechanism of a series of (4,8)-connected Zr-tetracarboxylate-based MOFs by altering the substituents on different positions of the organic linkers. Different ligand rotamers give rise to three types of structures with flu, scu, and csq topologies. A combination of experiment and molecular simulation indicate that the steric hindrance of the substituents at different positions dictates the resulting MOF structures. Additionally, the controllable formation of different structures was successfully implemented by a combination of linkers with different steric effects at specific positions.

Solvothermal reaction of a tetracarboxylic acid with Ba(NO3)2 afforded a barium–organic framework whose single crystal X-ray structure was characterized to have I2O1 connectivity and 1D channels 15.1 Å in diameter. The luminescence intensity of this MOF can be modulated by ion exchange.