That depends on what you are trying to achieve? Sure, the captured CO2 is still CO2, but you can put it in an empty gas field somewhere and the net effect on atmospheric CO2 (which is what we are concerned about with regards to climate change) is the same as if you had split apart the molecules.
The process described in the paper can be used only after CO2 is separated from the air, not instead of it.
Nevertheless converting CO2 into a solid reduces the volume one thousand times and makes its storage very simple.
I doubt that there could be found enough subterranean spaces that can be sealed well enough, in which to pump as much CO2 as it would be needed to reduce the concentration in the air.
Every American uses around 400 gallons of gasoline and 12,000 kwh electricity per year. So if you put a tax of $2 on each gallon of gasoline and 7 cent on every kwh electricity, you would finance that.
And once it scales, it will be cheaper and cheaper, jut like most other products. With a 10 percent price reduction per year, it would be $620 per person in 10 years, roughly the same as an internet bill.
In the rest of the world it's even cheaper. The average person in the world could be offset for $400 now.