Generally, you cannot deduct a charitable contribution of less than your entire interest in property. A contribution of the right to use property is a contribution of less than your entire interest in that property and is not deductible.
For example, you own a 10-story office building and donate rent free use of the top floor to a charitable organization. Because you still own the building, you have contributed a partial interest in the property and cannot take a deduction for the contribution.
Similarly, you cannot claim a charitable deduction for donating a week at your vacation home to be auctioned off at a fundraiser.
For example, Sue Smith owns a beach house that she frequently rents out. She contributed the right to use it for a week to her Church. At the auction, her church received and accepted a bid from John Jones equal to the fair rental value of the home for 1 week. Sue cannot claim a deduction because of the partial interest rule. John cannot claim a deduction either, because he received a benefit equal to the amount of her payment.