Hi,
The FEX is supported on the Nexus 7000 as from NX-OS 5.2(1), but it's complicated on this platform depending upon which line module you're connecting the FEX to.
Table 3 in the Supported Device Hardware section of the Nexus 7K release notes should give you what you're looking for. What you'll see there is that the N2K-C2232PP-10GE FEX is supported on the N7K-F248XP-25E I/O module as from NX-OS 6.1(2).
Regards