Herein, to investigate the effect of introducing an additional aluminium atom to the framework, MFI models with two aluminium atoms per unit cell, i.e., with an aluminium pair, were considered. A total of 20 models containing aluminium pairs were considered, with at least one of two T-sites occupied by aluminium located in the T12 site. The T12 site is located at the intersection of the straight and sinusoidal channels and is considered in the litera-ture as one of the most commonly occupied T-sites by aluminium in MFI. Aluminium pairs that are separated by one and two T-sites were considered, termed as next-nearest neighbour (NNN) and next-next-nearest neighbour (NNNN) pairs, respectively. The nearest neighbour aluminium pair, i.e., a pair separated only by only one framework oxygen atom is not considered due to the Löwenstein rule. Altogether, 12 NNN and 8 NNNN aluminium pairs were modelled and their Al chemical shifts calculated. For each aluminium pair, two water loadings were adopted (0 or 17 water molecules). A detailed description of the aluminium pairs is provided in Table †. Fig. The effect of introducing an additional aluminium atom into the framework on the Al chemical shift of the original aluminium atom located in the T12 site. The effect is plotted as a function of the distance between the aluminium pairs, forming the next-nearest neighbour (NNN) and next-next-nearest neighbor (NNNN) pairs. The black line represents the chemical shift of an isolated aluminium located in the T12 site. The variation in chemical shift is plotted for both dehydrated (left) and fully (17 waters) hydrated models (right). Fig. depicts the impact of introducing an additional Al atom into the framework on the chemical shifts of aluminium at the T12 position, comparing the effects in both dehydrated and hydrated frameworks. In the dehydrated framework, the average absolute change in the chemical shift due to nearby aluminium averages to 1.3 ppm, compared to 0.8 ppm in the fully hydrated MFI framework. Specifically, the largest increase in chemical shifts is observed in the dehydrated state, reaching 1.9 ppm, whereas in the hydrated state, it can increase by as much as 2.2 ppm. Conversely, the decrease in chemical shift appears to be more pronounced, falling by up to 4.7 ppm in the dehydrated framework, and as much as 2.2 ppm in the hydrated case. These findings are consistent with those reported by Dědeček et al. , who observed a maximum negative displacement of 3.8 ppm and positive displacement of 1.5 ppm from the isolated value in dehydrated cluster models with NNN aluminium pairs.