In general, I recommend avoiding use of non-determinate "this" as a pronoun and instead replace it with a determiner, "this what". In your example, replace the potentially ambiguous "this" with "this issue":
"Thank you for bringing this issue to my attention. We will take care of this issue this afternoon."
Doing so eliminates the double "this" and avoids the potential for "this" to refer to anything, including the potential interpretation, "We will take care of my attention this afternoon."
See this article for a more in-depth explanation on why an ambiguous "this" pronoun can be dangerous and should be avoided.