The controllable growth of non-centrosymmetric metal organic framework (MOF) beyond the conventional micrometer crystal dimensions would represent an enabling step in the development of MOF-based devices for coherent nonlinear optics. This goal has been elusive so far, as MOF crystal typical self-assemble under metastable synthesis conditions that have several competing crystallization pathways open, and only a modest amount of external control over the crystal nucleation and growth rates is currently possible. We overcome some of these issues and achieve the controlled growth of large single crystals of the non-centrosymmetric MOF Zn(3-ptz)<sub>2</sub>, with surface areas of up to 25 mm<sup>2</sup> in 24 hours, in a single solvothermal reaction with <i>in-situ</i> ligand formation. No additional growth steps are necessary. We carry out a mechanistic study to unravel the reaction steps leading to the self-assembly of Zn(3-ptz)<sub>2</sub> crystals, by identifying and isolating several intermediate crystal structures that directly connect with the target MOF, and reversibly interconverting between them. We identify the synthesis parameters that control the size and morphology of our target MOF crystal and model its nucleation and growth kinetics using <i>ex-situ</i> image processing data. Our work is a step forward is understanding and controlling the factors that stabilize the growth of high-quality MOF crystals with sizes that are relevant for coherent optics, thus untapping possible applications of metal-organic frameworks in classical and quantum communication technology.
Millimeter-Scale Zn(3-ptz)2 Metal–Organic Framework Single Crystals: Self-Assembly Mechanism and Growth Kinetics
