d4 means positional play. it means less aggressivnes then e4 and it means patience. compared to e4 where after e5 one has a clear target and the choice to attack it (the unprotected e5 pawn) d4 met with d5 has no such weekness. perhabs that is the reason why the Queen´s Gambit is such a popular openig. but lets look at it.
d4!
Play pawn to d4.