Rail to Rail op Amp circuit
You are trying to create a divider with a voltage follower. The inverting and non-inverting inputs need to be swapped.







simulate this circuit &ndash; Schematic created using CircuitLab

Figure 1. Passive 4:1 voltage divider.

The circuit of Figure 1 should do the trick for you. 


R1,2 and 3 can be replaced by any combination of resistors to give you three times the value of R4. 
R4 needs to be a factor of ten lower than the input impedence of your 0 - 3 V ADC so that the ADC doesn't load the divider too much.