how friction is non conservative in nature. explain with examples

Look up the definition of non-conservative. FRiction is non-conservative only in a macro sense, if you go to the actual motions of the molecues absorbin the "frictional energy", they end up having motion, or vibration.

Friction is a non-conservative force in the macro sense, because it mechanical energy is not conserved. If one ignores some of the degrees of freedom (such as the trillions of motions in the molecules), it is conservative, but frankly, that is a very large math issue.