[Zr₆(μ₃‐O)₄(μ₃‐OH)₄](1‐adamantanecarboxylate)₁₂]: a model for extrinsic “defect‐engineerable” porosity

Abstract The molecular zirconium‐oxo cluster with 1‐adamantanecarboxylate of ideal formula [Zr 6 O 4 (OH) 4 (AdCA) 12 ] (AdCA=1‐adamantanecarboxylate) has a near spherical shape with a hydrophobic “shell” of bulky rigid adamantyl groups. The use of formic acid as a modulator and a large excess of the HAdCA were found to be crucial for its reproducible synthesis and the formation of ~100‐150 μm well‐formed rhombohedral single crystals. Crystallization in the presence of formic acid leads, however, to ligand‐substitution defects (1‐2 out of 12) which were quantified by thermogravimetry and NMR. A defect‐engineering with a higher defect ratio in such oxo clusters is a promising approach aiming at extrinsic porosity.