This absolutely will not work. Sorry about that . You’re just going to get some confused shopkeepers if you try.
What you can do, however, is use Alipay. Download the Alipay app. When setting it up, it’ll ask if you want to use Alipay International - if you select this option you can add your Monzo (or other MasterCard/Visa etc) and buy some yuan. It’ll operate as a pre-pay version of the app. Keep in mind you won’t be able to refund any balance but you get the Chinese experience of how people spend money.
If you click below, there’s an excellent guide me and a few others have put together with all you need to know about Alipay / payments in China.
Have a great trip.