The 29-year-old Belgium international left-back joined the Seagulls on a season-long loan deal last summer having fallen out of favour at his parent club side West Brom.
Pocognoli made 20 Championship appearances for the club and scored one goal as they secured automatic promotion to the Premier League.
It was thought that the player would opt to sign a permanent deal at the Amex Stadium when his Baggies contract expires at the end of June, but he has instead decided to return to his homeland with former club Liege.
On confirmation of Pocognoli's exit, Seagulls boss, Hughton, told the club's website: "Seb was an absolute pleasure to work with and he was yet another key member of the squad that clinched our promotion.
"I am pleased he has confirmed his future and joined Liege, and on behalf of everyone at the club, I would like to thank him for his efforts during his time with us and wish him all the very best for the season ahead and into the future."