The 741 was designed to operate on +15 and -15 V supplies and process signals between +10 V and -10 V. It can be run in single supply designs but it has limitations. The input common mode range does not extend down to 0 V or up to +5V. In fact, it is so narrow that you will have only about 1 V of operating room. Also, its output does not swing within 1 or 2 volts of the rails, so again the operating range is extremely limited. All of this is in the datasheet, which you must read.
Separate from that, even if you had a modern rail-to-rail opamp it would not drive the relay well, if at all. The FET is configured as a source follower, and the source will never be more than 2 or 3 volts above ground. If the relay has a 5V coil, it probably will not pull in.
And finally, the circuit is not complete. I assume the temperature sensor connects to J1, but you do not indicate that, or what the 3 pins do. Without this, a complete circuit analysis can not be done.
ak