Linker-Connectivity Regulated Competitive Synthesis of Zirconium-Based Metal-Organic Frameworks

Zirconium-based metal-organic frameworks (Zr-MOFs) have garnered significant attention owing to their exceptional stability and tunable structures. While tremendous progress has been made in the challenging synthesis of crystalline Zr-MOFs, the competitive formation of Zr-MOFs in the presence of multiple organic linkers remains elusive. In this work, using 1,4-benzenedicarboxylic acid (H₂bdc) and biphenyl-3,3',5,5'-tetracarboxylic acid (H₄bptc) as exemplary ligands, we systematically explore the competitive synthesis of Zr-MOFs. Through combined techniques of PXRD, NMR, SEM, and porosity characterizations, we elucidate the critical roles of solvents, acidic modulators, linker molar ratios, temperature, and reaction time in the formation of the final products. Specifically, we reveal that the addition of formic acid (FA) or acetic acid (AA) remarkably facilitates the formation of Zr-bptc, whereas benzoic acid (BA) favors Zr-bdc (UiO-66) as the predominant product. This may be a general rule, as a similar trend was observed when Zr-bptc was substituted by other Zr-MOFs comprising a different tetracarboxylate or tricarboxylate linker. In contrast, the influence of other synthetic parameters is marginal but cannot be neglected. These findings provide new insights and experimental evidence for the competitive formation of Zr-MOFs and may guide the future design and synthesis of novel Zr-MOFs.