Can I freeze citrus fruits?

Yes.  Remove the rind, divide the fruit into sections, and remove seeds. Adding syrup or sugar to the fruit will help sweeten it. When frozen, unsweetened fruits lose quality faster than sweetened ones.
 
Pack the fruit in a sealable plastic bag or airtight lidded container. Press down on the bag prior to sealing it in order to remove as much oxygen from the bag as possible. This will help prevent freezer burn. Packing the container rather tightly will displace oxygen and prevent freezer burn. However, leave an inch or so of head space in the container to accommodate the expansion that occurs when high-moisture foods freeze.
Frozen citrus fruit  should be consumed within 6 months.
 
Source(s):
National Center for Home Food Preservation "Freezing: Citrus Fruits"
Ohio State University "Freezing Fruits"