Two-step procedure for binding of host 1: The metal oxide substrate was dipped in a solution of propiolic acid (10 μl in 10 ml MeCN) for 30 min. After this, the substrates were dipped in pure MeCN for 5 min to remove excess propiolic acid, then dried under a stream of N 2 . The samples were subsequently immersed in a solution of 1 (0.7 mM) in DMF (10 ml) containing NEt 3 (20 μl) for 1 h. The substrates were then soaked in pure DMF (15 ml, 5 min), pure MeOH (10 ml, 5 min) and finally dried under a stream of N 2 .