‰ is increased. To illustrate how materials with "better" parameters will exhibit a better selectivity, we imagine a hypothetical catalyst, which would be obtained from VPP, increasing its pore volumes by 50 % (in both fresh and activated materials) and decreasing its activation energy of conductivity by 50 %. The VPPmodified material, shown as the green dashed line in Fig. , would provide an acrylic acid selectivity ca. 3 times higher than that for VPP. For this gedankenexperiment, we assume that all other primary features of the catalyst remain unchanged. Finally, we note that the models derived by MT-SISSO are expected to hold for catalysts obtained as modification of the vanadium-based catalysts as well for other (new) materials as long as the reactivity is governed by the same processes governing the catalytic performance in the nine materials of our data set. However, for regions of the materials space containing catalysts very different from those in the data set, the MT-SISSO model might need to be re-trained with more data. This calls for a systematic experimental exploration of the materials space, i.e., addition information at (𝑑 : , 𝑑 , ) regions whose experimental data are missing, at present.