Mechanistic insights into metal-organic framework thin film growth from microkinetic analysis of in situ X-ray scattering data

Abstract

Metal-organic framework (MOF) thin films offer exceptional properties for diverse applications, yet the mechanisms underlying MOF crystallization are not fully understood. Knowledge gaps remain regarding the nucleation and growth mechanisms of these highly porous, crystalline materials under dynamic evaporative conditions. Here, an in situ grazing incidence wide-angle X-ray scattering (GIWAXS) combined with a microkinetic model is used to probe the dynamic growth of MOF films. We show that while most high-order oligomers are produced in the solution phase, the key parameters that control thin-film growth are autocatalytic synthesis of secondary building units (SBUs) followed by physisorption on silicon wafer substrate, exponential growth due to evaporation-driven step growth, and transition to the stationary phase due to mass-transfer-limited growth. Importantly, this study demonstrates the applicability of this microkinetic modeling framework to predict film properties across a range of temperatures and reactant concentrations, allowing for rational design of MOF thin films.