Metal-doped amorphous silicates have been used extensively in industrial applications. For example, the Phillips catalyst, CrO x /SiO 2 , is used to produce more than one third of the world's polyethylene; 1,2 WO x /SiO 2 has long been used in the Phillips Triolefin Process for the large-scale production of ethylene and 2-butene from the metathesis of propene. The advantage of these heterogeneous catalysts stems from a simple production procedure of the material with dispersed metal centers, and the high activity of distorted catalytic sites embedded in the amorphous silicate matrix. Despite large-scale applications, the active sites and reaction mechanisms are not well understood due to the inherent heterogeneity in both composition and structure. Common experimental characterization can only provide information about average site properties, but it cannot discriminate the most active sites, which represent 1-10% of the total and ultimately drive the effective reaction rates, from the rest. Therefore, catalyst improvement often relies on a trial-and-error approach rather than rational design.