Einsteins equation indicates that there will be no photoelectric emission unless hf > ⌀. The frequency that is just large enough to liberate electrons, f0, is called the threshold frequency, so ⌀ = hf0
If hf0 = ⌀, doesn't that mean the kinetic energy is equal to 0 and therefore the electron is never released?
It depends what you mean by "released". At the threshold frequency, the electrons are "released" from the atoms they were previously bound to. But as you say, there is no left over energy from the photon to give them any kinetic energy. As such, they will recombine with the positive ions in the metal, and will never actually be "released" from the metal itself.
Photo electric Effect is that phenomena in which current will produced due to ejection of electron when the in coming photon frequency will be greater then the threshold frequency of the that matel. remember the threshold frequency will be diffenent for different elements. and if threshold frequency will be equal to the incoming photon frequency then k.e will be zoeo...
At the threshold frequency the electrons are just released from the surface of the metal, since they have no kinetic energy to move away from the metal surface they will just attach to the metal again.