An equimolar reaction between ZnEt₂ and 1,3,4,6,7,8-hexahydro-2H-pyrimido[1,2-a]pyrimidine (hppH) results in the formation of EtZn(hpp) (1) which crystallizes as a trinuclear agglomerate with the guanidinate ligands spanning 4-coordinate Zn centers. Exposure of a pre-formed THF solution of 1 to undried air leads to a ZnO-incorporating derivative 1₄·ZnO, while an analogous experiment with CH₂Cl₂ as solvent leads to a novel tetranuclear mixed aggregate formulated as [EtOZn(hpp)]₂[ClZn(hpp)]₂ (2). The composition of 2 indicates that its formation proceeds via a complex multi-step reaction route that involves not only the oxygenation of ZnEt moieties, but also the activation of CH₂Cl₂, causing the transfer of a chloride anion to the Zn center. Compounds were characterized by ¹H NMR spectroscopy and single-crystal X-ray diffraction analysis.

The layered 2D MOFs, owing to their enhanced flexibility and tunability, have recently emerged as a promising alternative to the 3D microporous MOFs in the quest for novel responsive functional materials. However, maintaining the simultaneous control over self-assembly of molecular building blocks as well as ordered stacking of MOF layers poses a significant synthetic challenge. We report on the controlled 2D MOF formation based on a case study of solvent-templated growth of a series of 2D Cu(II)–carboxylate MOFs varying in stacking modes and distances using a diffusion-controlled MOF deposition approach in various solvent mixtures. Moreover, we demonstrate the structural dynamics of the developed 2D MOFs involving both in-plane and out-of-plane movements of the individual 2D layers triggered by solvent exchange, which allowed for selective postsynthetic transformations between the developed 2D MOFs. We also investigated the gas adsorption properties of the developed MOFs, which demonstrates a remarkable crystal size effect on the N₂ adsorption capacity using a model 2D MOF system.