I want to create a wither rose farm in the middle of the void using an enderman farm, but it is very important that the endermen cannot teleport anywhere. Therefore, I want to have the bridge towards the farm made of a block that endermen cannot teleport to, and I have an excess of leaf blocks. Can I use them?
I believe Enderman can teleport to non-waterlogged leaf blocks, though according to the Gamepedia Wiki;
"Endermen never teleport into waterlogged blocks. Exceptions are carpet that is not above a block made of a movement-blocking material, lily pads and snow layers stacked 10 deep or more, as their materials are not flagged as blocking movement even though the blocks themselves do so."
So prehaps water-logged leaves could work with what you want to build.