Understanding how different factors affect the electronic properties of metal-organic frameworks (MOFs) is critical to understanding their potential for catalysis and to serve as catalyst supports. In this work, periodic dispersion-corrected quantum mechanical calculations are performed to assess the catalytic activity of different Zr6 vs Zr12 MOFs for the heterogeneous catalytic hydrolysis of the chemical warfare agent sarin. Using a comprehensive series of extended periodic models capable of capturing long-range sarin/water/framework interactions in both Zr6 and Zr12 MOFs, the effects of numbers and morphologies of defective sites, as well as ZrIV substitution with heavier CeIV, are thoroughly investigated. Our calculations show that hydrogen bonds involving both metal-oxide nodes and organic linkers can play important roles in the catalysis. Insights derived from this work should inform the design and realization of more effective and robust next-generation MOF-based heterogeneous catalysts.