2048 was a super popular puzzle game in 2014. There are about a billion clones making it hard to fine a solid, ad free implementation. Here are a few that I like.
Ekstar 2048 - Simple implementation of the basic game with no ads and a refreshing color scheme.
2048 classic - traditional in all ways, game play and color scheme, no ads.
2048/3: improved hybrid - A bit of a blend of 2048 and 3s. I like it better than 2048, but I suppose that comes down to taste. no ads.
Threes! - this is what inspired 2048. But frankly I think the original isn't as good as what came later. But if you've never played 3s it's worth seeing how this all evolved. It does have ads, or you can pay the astronomical price of $6 for the ad-free version.