Is it possible to use bitcoin core on Mac OS Sierra saving the data on the network drive?
Core (more specific levelDB, the database library used) does not support network drives.
Also, the UTXO access (chainstate) must be as fast as possible and should run on an internal drive, ideally an SSD.

If you need to reduce/transfer disk usage, there are two main possibilities:

Pruning

Add prune=550 to you bitcoin.conf (or startup with -prune=550) to reduce the kept block data to a minimum. Your node will still do full validation but does not server old historical blocks to other peers.

Symlinks

Symlink the blocks directory is possible. Check https://en.bitcoin.it/wiki/Data_directory#Transferability