Why can ESPO create frameworks?
Both the Procurement Act 2023 and the Public Contracts Regulations 2015 permit contracting authorities, such as ESPO, to establish frameworks in order to set the terms for any contracts that might be agreed going forward.  
Contracting authorities can award suppliers a position on their frameworks, if they are suitable and compliant to the criteria of the specific framework and the Procurement Act or Public Contract Regulations (as applicable).