Summary
All of the QR code generator workflows I've come across use a dependency, such as an external installation, embedded app, or web service. Given that MacOS can create QR codes natively, that's what I did with this workflow.
Usage
I've configured this to use two different keywords, qrc & qrp. The qrc keyword creates a QR code that copied to the clipboard. The other keyword, qrp does the same thing, except at the end it'll open the QR code in Preview to allow saving as an image/pdf.
When using either qrc or qrp without a parameter this workflow will attempt to use text contained on the clipboard. This same flow is followed if you set a hotkey for the selection and nothing is selected.
Download
https://github.com/TorreyBetts/Alfred-QRCode/releases/download/v1.0.3/QR.Code.alfredworkflow
GitHub
https://github.com/TorreyBetts/Alfred-QRCode