Microporous Titania Crystals with Penta-oxygen Coordination

Porous materials play an important role in various chemistry applications. Here with a large amount of data from global potential energy surface calculations of titania TiO2, we identify a class of new microporous TiO2 crystals, TiO2(TB), featuring the largest known pore size (5.6–6.7 Å) for TiO2 crystals and an unprecedented [TiO5] trigonal bipyramid building block. Their pores are constituted by six- and eight-[TiO5] rings with the six-member ring being the most stable. While [TiO5] coordination is traditionally regarded as an unstable unit for titania, the porous TiO2(TB) are in fact energetically more stable than the common TiO2 rutile phase and are also found to be kinetically stable at high temperatures as evident from ab initio molecular dynamics simulation. The strong ionic bonding in the Ti–O lattice is the key to stabilizing these porous materials to compenstate for the weak covalent bonding in the [TiO5] building block. By evaluating the Li-insertion energetics and structrual parameters, we predict that these microporous TiO2 crystals are good candidates for Li-ion anode material.