Ambient Pressure Fabrication of Cu x Zn 1– x (BDC) ₂ DABCO Thin Films Through Spin-Coating and Their Temperature-Dependent Structural Development

Metal-organic frameworks (MOFs) have garnered widespread attention due to their inherent tunability and consequent applications for a variety of technologies. Spin-coating is a fast and cost-effective method for new materials discovery, which yields less chemical waste than traditional solvothermal, dip-coating, or other layer-by-layer synthesis methods. The purpose of this work is to expand the types of supported MOF thin films to include a bimetallic thin film and to understand the effects of temperature on the MOF size and coverage, as well as the ranges and limits of composition. Because the pillared MOF archetype M₂(BDC)₂DABCO, where (M = Cu²⁺, Zn²⁺), is known to exist as copper and zinc MOF analogues; therefore, it was chosen for incorporating both metals into a single structure. For the thin films, MOF growth increased with temperature until solution instability (>52 °C). Thin films are sensitive to metal precursor selection; the Zn-MOF thin film would not grow using Zn(NO₃)₂ as the precursor; however, Zn(OAc)₂ resulted in the cogrowth of ZnO nanoparticles within the MOF. The amount of Zn²⁺ incorporated into the Cu-MOF can be changed by altering volume ratios between Cu(NO₃)₂ and Zn(NO₃)₂ precursors in solution. Understanding these parameters for a bimetallic MOF thin film provides a flexible methodology for surface-mounted thin films for future discovery and advancement.