So long as you are in the clan when the clan leader uses the 2xp then yes you will get the 2xp hours regardless of whether you are a premium or a free member. However, your clan leader does have to push a button to have the 2xp distributed to the clan. Many clans will hold on to the 2xp hours that they have acquired and distribute them later. Personally I distribute them right away unless I know that a 2xp weekend is coming and then I'll distribute them on the 2xp weekend. This way my clan members get to enjoy a few hours of 4xp instead.