Free of nicotine? I strongly assume that would only be possible with selective breeding or biotech, and would not be at all economically viable due to biological reasons. Nicotine is the main defence of Nicotiana tabacum against bugs and diseases. It is a very poisonous thing, after all.
The fermentation and further processing of tobacco is a fiddly thing, so I assume without a big financial incentive a search for a substitute which has a favourable flavour and a mild mouth-feel will not even commence. And, as others pointed out: it’s still toxic to inhale smoke.
There are plenty of herbs you could smoke without nicotine, but it will raise a lot of eyebrows. I used to have fun with that. But I wouldn’t have cigarettes made with completely legal herbal filling on me nowadays when travelling. 
