The Northern Irishman dropped the champion in the fifth round in a near-perfect display, but despite being unable to finish off the Spaniard, the three judges scored the fight 119-108, 119-108 and 118-11 all in the 27-year-old's favour.
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Like in their first contest in February 2013, which Frampton won by a ninth-round stoppage, Martinez was relentless in his offensive approach, but he was often picked off by a more composed challenger.
Frampton floored his opponent with a short right with 20 seconds remaining in the fifth, but Martinez was not discouraged by the knockdown and he started to come back into the fight at the start of the championship rounds.
However, he only found limited success, and it was Frampton who ended the night on the front foot to deservedly become world champion in just his 19th professional bout.