Considering that there are two chemically-distinct sites based on the probe molecule studies, two families of sites with distinct EFG parameters, 𝜂 0 𝑖 and 𝐶 𝑖 𝑄,0 , and independent degrees 𝜀 𝑖 (𝑖 = 1,2) of Czjzek-noise are incorporated into the ECM. To reflect the relative amounts of Brønsted vs. Lewis acid sites found from the N NMR studies on the material contacted with py, the weighting of signals was constrained to a 6:4 ratio for the respective sites.