We aim at the construction of dark energy models without exotic matter but with a phantom-like equation of state ( an effective phantom phase ) .
The first model we consider is decaying vacuum cosmology where the fluctuations of the vacuum are taken into account .
In this case , the phantom cosmology ( with an effective , observational \omega being less than -1 ) emerges even for the case of a real dark energy with a physical equation of state parameter \omega larger than -1 .
The second proposal is a generalized holographic model , which is produced by the presence of an infrared cutoff .
It also leads to an effective phantom phase , which is not a transient one as in the first model .
However , we show that quantum effects are able to prevent its evolution towards a Big Rip singularity .