Liping Huang, Department of Chemical and Biomolecular Engineering and Department of Physics, North Carolina State University, Raleigh, NC 27606, Erik E. Santiso, Department of Chemical Engineering, Massachusetts Institute of Technology, Cambridge, MA 02139, Keith E. Gubbins, Chemical and Biomolecular Engineering and Center for High Performance Simulation (CHiPS), North Carolina State University, Raleigh, NC 27695-7905, and Marco Buongiorno Nardelli, Department of Physics, North Carolina State University, Raleigh, NC 27695.
Periodic mesoporous organosilicas (PMOs) have hexagonal pore arrangement in the mesoscale and crystalline pore wall with alternating hydrophilic silicate layers and hydrophobic organic layers. The silicate layers provide the rigidity to the materials and the organic layers can be functionalized for potential applications including hydrogen separation and storage. By using first-principles density functional theory calculations, we demonstrated the chemisorption of carbon monoxide on these PMOs materials, while hydrogen molecule interacts with PMOs only through weak van de Waals force. The selective adsorption of CO in PMOs can be used for hydrogen purification, to prevent poisoning of the electro-catalysts used in fuel cells. On the other hand, the interaction between H2 and PMOs can be modified by metal atoms. Metal decorated PMOs have been designed for efficient hydrogen storage. Our studies show that the bonding between metal and hydrogen is of a combination of chemical and physical adsorption, which is essential for reversible hydrogen uptake/release. Car-Parrinello molecular dynamics simulations demonstrate that these systems are stable and exhibit associative desorption of H2 upon heating without breaking the bond between PMOs and metal. This fulfills another requirement for reversible hydrogen storage.