Schmitt Trigger does not go to ground
Reduce the value of R4, to allow more base current in Q1, and therefore more collector current.

If you want a comparator, it is much better to use a chip designed for that function, than to use an ancient op-amp.  If you look at the LM741 datasheet, you will see that the 741 can't get its output closer than a couple of volts to either power supply pin.