Carbondioxide + 4 molecules of hydrogen gives----------------

Well, the only reaction that I can think of it that one:

CO_2 + 4H_2 \rightarrow CH_4 + 2H_2O

But this reaction must be very endothermic (absorb a lot of energy for it to occur) [and I don't think the yield is worth it]

I doubt anyone would do such a reaction.