Double quote using expression in a template

I need to add double quoted (") value in json template using an expression.
Double quoting whole expression is not an option. I need to add null (non quoted) too
Below function works as expression in a virtual coulumn

But when it cretaes a json file it adds an extra slash (/) which fails json parse…

Any help?

Why do you explicitly need a double quote in your JSON?

Can we form a json template without double quote? (")