Structure and reactivity of single site Ti catalysts for propylene epoxidation

•Selectivies are quantitatively correlated to the coordination number of TiO.•The single-site, 4-fold coordinated TiO2 favors high PO selectivity and H2 efficiency.•Atomic layer deposition was used to precisely deposit a uniform layer of TiO2.•Uniform single-site Ti facilitates alternation of TiO coordination using calcination.