Yes, security deposits for hotels or car rentals can be paid with your Pleo card. The amount for the transaction will appear under Expenses as "pending" and once the merchant approves the transaction, it will be settled and deducted from your Pleo wallet balance.
As Pleo is a pre-paid card, you will always have to make sure your Pleo wallet is loaded with enough funds to cover the security deposit amount.
Note: Your authorisations will not be exported - be sure to let your bookkeeper know! Read more about authorisations vs presentments in the help center :)