I have a temp job (9 months) in another state, and have rented an apartment to stay in during the week. Can I take the rent off fed taxes as an expense?

No. Personal rental expenses are not deductible for federal taxes and you can no longer deduct unreimbursed business expenses.

Some states do offer a rental deduction. Most such deductions are limited to residents. It’s possible you may qualify for a state rental deduction (if there is one) if you were a part-year resident. You would have to clarify your situation.