I am posting this as an answer but it is not an answer to
What can i put around the doorknob to keep the dog from scratching the door
Shelf paper or any other thing you put on the door is a Bandaid not a cure.
The proper and humane way to address the problem of your dogs separation anxiety is to seek knowledge and help from an animal professional about how to teach or train or deal with the issue.
- (Maybe your dog feels like it is being abandoned and locked up and does not know if its best friends will be back for him/her. Imagine if this happened to you day after day after day. Or maybe it has an overwhelming desire to be as close to you as possible ALL the time)
Dog are very intelligent and very trainable, (as are most people) you can avoid the need to modify your door, and make your dog healthier and happier, by learning how to train your dog, and yourself, or how to address the reasons for its separation anxiety.
Start by researching the internet and reading articles like
Take a class WITH your dog so you and it can learn to communicate and you can learn how to train your dog.
It is a two way street, you must learn so your dog can learn.