Analysis of H2 adsorption data collected at 77 K revealed that Cu2.7-MFU-4l adsorbs 2.09 mmol/g at 1 mbar of H2, nearly double the capacity measured for Cu2.2-MFU-4l under the same conditions (Figure ; see also Table for a comparison of reported copper(I) loadings in various Cu I -MFU-4l samples prepared in the literature). From this uptake, we estimate that approximately 89% of the copper sites in the material are copper(I), which is one of the highest levels of copper(I) incorporation reported for Cu I -MFU-4l to date. Analysis of 77 K N2 adsorption data revealed that Cu2.7-MFU-4l has a high BET surface area of 4160(40) m 2 /g (Figure ) that exceeds previously reported values for Cu I -MFU-4l (347-4000 m 2 /g, see Table ). Thermal decomposition profiles collected under dry N2 and O2 revealed that the material is stable until approximately 400 and 280 °C, respectively, under these gases (Figure ). We found it is also possible to prepare Cu I -MFU-4l via the above route using hydrated CuCl2 in dimethylsulfoxide without the exclusion of air or water (see Section 2 of the Supporting Information for details). The resulting material exhibits a similarly high H2 capacity of 1.94 mmol/g at 77 K and 1 mbar (Figure ).