[sidewndr46]

You have suggested in the same comment that somehow we will have nearly limitless carbon-negative energy but also that the amount of energy to get to Mercury is too high to make the trip worth it. This does not follow from the initial assumption.

[adastra22]

Why spend X/kg to get something from mercury when you could spend 1/4 or 1/8 as much to get it from the asteroid belt?

[ben_w]

A lot more Mercury than sum of all asteroids. On the scale of "this century" this may only matter for von Neumann probes building a Dyson swarm, but that's not a 0% possibility and you did ask for a reason.