The freezing point is far below that of water. Exactly what that freezing point is depends on the proof of the liquor.
Water freezes at 0°C (32°F) and the freezing point of ethanol alcohol is -114°C (-173.2°F). Alcoholic beverages are a mixture of both alcohol and water (with sugars and other additives in some distilled spirits) so the freezing point of all of you alcoholic beverages is somewhere in between. The exact freezing point of vodka, gin, tequila, rum, whiskey and the myriad of liqueurs is dependent on its proof, or alcohol per volume. The lower the proof, the warmer the freezing point: the higher the proof, the colder the freezing point.
* 24 proof liquor freezes at -6.7°C (20°F)
* 64 proof liquor freezes at -23.33°C (-10°F)
* 84 proof liquor freezes at -34.44°C (-30°F)
These freezing points are much colder than the average home freezer will reach, so chilling a bottle in the freezer should not freeze the liquor inside. However, your freezer could get cold enough to freeze low proof liqueurs, beer and malt beverages. These low proof beverages will get slushy, and eventually freeze, if left in the freezer for too long and can explode leaving a big, frozen mess if it gets too cold.