No, this is maximizing net freedom. Pollution infringes on the rights of others... a libertarian solution would have been more efficient and penalized the source on a consumption basis (gasoline tax), but the incentive would be similar.
Here's a libertarian-ish analysis on the formerly proposed Washington state carbon tax: http://www.leolinsky.com/2016/11/06/carbon-tax-initiative-73...
I hope to erase a lot of extremist misunderstandings about freedom (as defined by the broadly interpretable nonaggression principle), because I think a lot of those on HN who currently identify with the Democratic Party would find they actually have more in common with independent, moderate libertarians (or even the LP) than they realize.