Synthesis and characterization of functionalized cerium and zirconium metal-organic frameworks as novel solid acid catalysts for hydrogen generation

To fulfil global energy needs and protect the environment, reducing fossil fuel use and increasing clean energy sources like hydrogen is essential. Hydrolysis of sodium borohydride offers a safe and cost-effective method for hydrogen production. This study focuses on the use of Ce- and/or Zr-based metal-organic frameworks (MOFs) and their functionalized materials with additives with different levels (5-15 wt%) (ammonium sulfate (AS), ammonium dihydrogen orthophosphate (ADHP), and phosphomolybdic acid (PMA)) as catalysts for the dehydrogenation of NaBH4. These functionalized MOFs exhibit improved catalytic activity compared to the MOFs. 15 wt% AS/NH2-UiO-66 displayed the highest hydrogen generation rate (377.8 mL H2 g−1 min−1). This study is the first to use Ce-BDC MOF (Ce-UiO-66) as a catalyst in NaBH4 hydrolysis. It produced 75 mL H2 within 15 min where the functionalized Ce-UiO-66 with 15 wt% ADPH achieved complete hydrolysis in just 9 min. Various factors affecting the reaction, such as catalyst mass, NaBH4 concentration, and reaction temperature were analyzed. XRD, FTIR, XPS, BET analysis was used to characterize these catalysts. The acidity of the functionalized MOFs, was assessed using pyridine as a probe. The rate constant, activation energy, enthalpy change, entropy change, and free energy of activation were estimated. These materials could pave the way for more effective catalysts in energy-related applications.