Base64 encodes groups of 6 bits into one of 64 8-bit characters. OP is doing the same, but with each character encoding 10bits.
The only problem is that these emojis probably require two bytes each (more?), so we’re encoding 10 bits into 16 bits (60% overhead) instead of 6 bits to 8 bits (33% overhead)
It’s a nice idea though. These are clearly easier to remember and compare. Just don’t expect emojis to take less space than base64.
You would hypothetically use this for a file where your communication channel is limited to emojis and text so... Twitter?
Here's a serious attempt at encoding arbitrary data into Unicode characters: