Do Catholics believe that Nephilim (Genesis 6:1-4) go to Purgatory?

I'm not Catholic, but I want to know the opinion and how Catholics who study the Word of God understand and interpret this passage of Genesis 6:1-4 that talks about a humanoid race of giants and if they went or can go to Purgatory. Purgatory is said to be a place or condition of temporal punishment for those who, departing this life in "the grace of God," are not wholly exempt from venial faults, or have not fully paid the due satisfaction for their transgressions. Do Nephilim have or had a chance to repent? Are they children of angels or mere mortal humans?