Adding phenanthrene as a co-guest let the second-generation crystalline sponge (2G-CS) method determine X-ray structures for 24 of 30 small, low-polarity C₁₅ molecules, mostly sesquiterpenoids. Under standard conditions, none of the 30 gave guest-containing crystals. Eleven of the 24 structures had not been reported before, including that of the liquid hydrocarbon longifolene. A chiral version of the cage gave the absolute configurations of five compounds.