With the goal of accessing a form of Cu I -MFU-4l featuring a greater number of copper(I) sites per node, and therefore higher gas adsorption capacities, we sought to optimize the synthesis of this material. For simplicity below, we denote Cu I -MFU-4l materials prepared via different routes simply as Cux-MFU-4l, where x specifies the total number Cu sites per node as quantified by ICP-OES analysis of the copper(II) precursor (e.g., the shorthand for Cu I -MFU-4l prepared via the literature route is Cu2.2-MFU-4l). Following extensive optimization, we found that treatment of Zn5Cl4(btdd)3 with 40 equivalents of CuCl2 in anhydrous dimethylsulfoxide at 60 °C yields a material with 2.7 Cu II ions per pentanuclear node, based on energy-dispersive x-ray spectroscopy and ICP-OES (Figures and). Two sequential additions of lithium formate monohydrate followed by a thermolysis sequence ending with heating at 250 °C afforded a material with the formula Cu2.7Zn2.3H0.9Cl0.7(btdd)3 (hereafter, Cu2.7-MFU-4l; see Section 2 of the Supporting Information for synthesis details and Figures S13, S27, S32, S35, and S36).