do you know if he will come为什么if后面用将来时

if如果引导条件状语从句,当主句是一般将来时,从句要用一般现在时,如:If it doesnt rain tomorrow,I will go to the zoo
但在这个句子中if(是否)引导的是宾语从句,不受时态的限制,
如:I wonder if she will come to see us tomorrow