It can't be done. You will still have to maintain water chemistry, perform water changes, and filter changes. The glass will have to be cleaned from time to time as well. Don't know if you ever noticed it, but treefrogs do dirty the glass. Take a wet, white paper towel and wipe it along the inside of the glass, then look at it. You will see the towel has picked up some of what the frogs leave behind. I don't believe there is any enclosure out there that is maintenance free.
You can, of course, have enclosures that require less maintenance. Large enclosures with only a few animals in them are easier to clean. Also they will need less frequent maintenance than a small enclosure with lots of animals in it.