I am researching on micropython to use for an IoT project for school using nodeMCU esp8266. one of the use cases requires the device to receive IR signal from an Aircon remote control and save it as well as being able to transmit this code using and IR LED. in circuitpython there is a library called pulseio that can do this function, but it is not available in micropython. can this library be imported into micropython?
In short No. 
It is very unlikely any CircuitPython library willl work straight over in MicroPython on your board. The main reason for this is that once the library starts to use UART or I2C the underlying implementation in CircuitPython is very dependent on other CircuitPython libraries which do not have equivalents in MicroPython.
It may be possible to find all these and re-implement them using standard MicroPython.
The decision point is if you can do that faster than finding a MicroPython library or example for your board to do the same thing OR if you should buy a CircuitPython compatible board instead.
Can circuitpython libraries be imported and used in micropython?