voltage divider and op amp
You have no feedback on your op-amp circuit and it is running with 'infinite' (well, very high) gain and basically operating as a comparitor.

The way the op-amp works is that if the + input is higher than the - input then the output will go high and vice versa.

Look up 'inverting op-amp circuit' and you will find plenty of circuits showing how to adjust the gain of the circuit to give desired results.