Figure shows Cu LMM Auger spectra of pristine CuBTC, IL@CuBTC, and IL@CuBTC after 12 cycles. According to the Cu LMM Auger transitions of different Cu species, we did not detect metallic Cu. The LMM transitions resemble those of Cu2O, stable across all studied samples with no sign of decomposition. Spectra of all elements present in the samples are shown in Figure S25, in which we observed a slight shift to higher binding energies after 12 thermal cycles, probably reflecting IL penetration in accordance with the low-temperature transition observed by XRD (see Figure ).