using hash function of (key||plaintext) instead of random value for IV for a protocol which implements AES under CBC mode, an $IV $(initialization vector) is required for each encryption.
Instead of picking the $IV$ randomly, is it advisable for us to set the $IV$ to be $\text{SHA1}(k||m)$ where
$k$ is the key, and $m$ is the $1^{st}$ 128 bits of the plaintext, e.g is this scheme semantically secure?
Any thoughts is welcome! Thanks!
No, it's not semantically secure.

Proof: select two plaintexts with identical initial 128 bits; and present them to the Oracle to be encrypted.  The resulting ciphertexts will also have identical initial 128 bits, hence the encryptor can be distinguished from something that generates random outputs.