Is this statement grammatically correct? [Thank you so much for your time and efforts; I really appreciate it]

Yes, it's correct. The semicolon is used to join two independent clauses whose meanings are very closely related and when you haven't already used a conjunction. The use of a semicolon is generally employed when the author wishes to communicate an extended pause (one that is lengthier than a standard comma) but doesn't wish to introduce a full stop and split the phrase into two distinct sentences altogether.