To provide as detailed picture as possible of the ZIF-inorganic glass interface, differential analysis of the PDF (dPDF) data was also carried out. This methodology has been already applied in Zr-MOFs to unveil local structural transitions or oxocluster structures. Typically, dPDF consists of subtracting the PDF of the pristine MOF from that of the modified material using a normalisation constant to minimise the residual at positions where the PDFs should be identical, such as at the C-C, C-N and C-O linker correlations. However, deciphering correlations at the interface glass-MOF is even more challenging, given the presence of at least three components: ZIF-8, the inorganic glass and the interface between this glass and ZIF-8. To simplify, we subtracted the D(r) of the physical mixtures from that of the composite, thereby minimising the correlation P-O (1.52 Å), which should be unchanged (Fig. ). However, the dPDFs were extremely difficult to analyse due to the complexity of this process.