We also already have genetically engineered carbon eating plants. Most of our agricultural crops have been genetically engineered (using selective breeding or molecular biology) to be much better at getting CO2 out of the atmosphere to produce carbohydrates than their wild counterparts. Unfortunately it seems that taking CO2 out of the atmosphere is like taking pee out of a swimming-pool: it's possible, but takes a lot of energy. Most crops compensate the increased energy cost for carbon uptake by reducing their defences against pests and droughts, which means they need to be subsidised with pesticides and irrigation (today produced mainly using fossil fuels).

It would be great if we could design trees that catch more CO2 than they need but, being an evolutionist, I'm not holding my breath. I imagine that even a small energetical efficiency increase would be a big evolutionary advantage and that plants are pretty close to their theoretical efficiency limit.

Of course IANAPNAPP (I Am Not A Physicist, Nor A Plant Physiologist), if you are please enlighten me.