The acidity of zeolites is primarily determined by the Si/Al ratio, which affects the concentration of Brnsted acid sites protonated oxygen atoms bridging Si and Al atoms and the strength of the acid sites. A computational study can be conducted to explore the effects of Si/Al ratio on the acidic behavior of zeolites. Here, we outline the steps for such a study:1. Model construction: Create a series of zeolite models with varying Si/Al ratios. For simplicity, consider a representative zeolite framework, such as the MFI ZSM-5 structure. Replace some Si atoms with Al atoms in the framework to generate models with different Si/Al ratios e.g., 10, 20, 30, 40, and 50 .2. Geometry optimization: Perform geometry optimization of the zeolite models using density functional theory DFT calculations. This step will provide the optimized atomic positions and lattice parameters for each Si/Al ratio.3. Acid site characterization: Identify the Brnsted acid sites in the optimized zeolite structures. These sites are characterized by an oxygen atom bridging an Si and an Al atom, with a proton attached to the oxygen. Calculate the concentration of Brnsted acid sites for each Si/Al ratio.4. Acidity calculations: Calculate the acidity of the zeolite models by determining the strength of the Brnsted acid sites. This can be done by computing the deprotonation energy DPE of the acid sites, which is the energy required to remove a proton from the oxygen atom. Perform DFT calculations to obtain the energy difference between the protonated and deprotonated states of the zeolite models.5. Analysis: Analyze the relationship between the Si/Al ratio and the acidity of the zeolites. Plot the concentration of Brnsted acid sites and the DPE as a function of the Si/Al ratio. This will reveal how the Si/Al ratio affects the acidity of zeolites.In general, as the Si/Al ratio decreases i.e., more Al atoms are incorporated into the zeolite framework , the concentration of Brnsted acid sites increases. This is because the substitution of Si by Al introduces a negative charge in the framework, which is compensated by the presence of a proton on the bridging oxygen atom. However, the strength of the acid sites as indicated by the DPE may decrease with decreasing Si/Al ratio, as the electrostatic interaction between the negatively charged framework and the proton weakens. This trend may not be linear, and the optimal Si/Al ratio for a specific catalytic application will depend on the balance between the concentration and strength of the acid sites.