The human mind can't generate enough entropy to create a secure brainwallet in that way. However, the reverse is permissible: use Bitcoin Armory or Electrum to generate a wallet, and then you should memorize the BIP39 mnemonic: https://github.com/bitcoin/bips/blob/master/bip-0039.mediawi...
Using the passphrase as both the salt and password for the PBKDF2 step strikes me as suspicious, but as I don't do crypto for my day job I'm not sure how bad this is (or isn't).
