It is possible to convert a QSFP or QSFP+ port to an single SFP or SFP+ port using the Quad to Small Form Factor Pluggable Adapter (QSA). However, in order for this to work, you'll need to configure the QSFP+ port into break-out mode to 4x10Gbps, similar like you would when using actual QSFP to 4xSFP break-out cables.

For OS10, the CLI for this action is:

interface breakout 1/1/7 map 10g-4x

This will break out the interface 1/1/7/ to 4 10Gbps links, which translates to these interfaces on the switch: 1/1/7:1, 1/1/7:2, 1/1/7:3 and 1/1/7:4:

show interface status ------------------------------------------------------------------Port Description Status Spe  ...