What we want is $\epsilon + 1 + 11$ .
Now what we don't want is a preceding 1 or a following one. So, $\epsilon + 1 + 11$ can be preceded by ( 0 + 10)* and $\epsilon + 1 + 11$ can be followed by (0+01)*.
So, the Regex becomes ( 0 + 10)*($\epsilon + 1 + 11$)(0+01)*