Is there a way to update the emoji font?
The font file you need to use a more recent version of is /System/Library/Fonts/Apple Color Emoji.ttc and is about 135MB.

The High Sierra version of the file and the process to install it to /Library/Fonts can be found here:
http://stephenradford.me/install-high-sierra-emoji-on-older-versions/

Note that the Emoji &amp; Symbol picker will not list the newer emoji added since your version of macOS. For that to work you would also need to update at least  /System/Library/PrivateFrameworks/CoreEmoji.framework and maybe some other files.