Unfortunately it is a bit tricky in practice, and still have a very significant global warming footprint[0]. You're never going to capture 100% of the CO4, and oil and gas wells tend to leak quite a lot of methane to the atmosphere.

So-called "blue" hydrogen only results in about 10% less GHG emissions than traditional "grey" hydrogen. It's something, but not big enough of a difference to actually be usable.

[0]: https://onlinelibrary.wiley.com/doi/full/10.1002/ese3.956