  Gas outflows are believed to play a pivotal role in shaping galaxies, as they
regulate both star formation and black hole growth. Despite their ubiquitous
presence, the origin and the acceleration mechanism of such powerful and
extended winds is not yet understood. Direct observations of the cold gas
component in objects with detected outflows at other wavelengths are needed to
assess the impact of the outflow on the host galaxy interstellar medium (ISM).
We observed with the Plateau de Bure Interferometer an obscured quasar at
z~1.5, XID2028, for which the presence of an ionised outflow has been
unambiguously signalled by NIR spectroscopy. The detection of CO(3-2) emission
in this source allows us to infer the molecular gas content and compare it to
the ISM mass derived from the dust emission. We then analyze the results in the
context of recent insights on scaling relations, which describe the gas content
of the overall population of star-forming galaxies at a similar redshifts. The
Star formation efficiency (~100) and gas mass (M_gas=2.1-9.5x10^{10} M_sun)
inferred from the CO(3-2) line depend on the underlying assumptions on the
excitation of the transition and the CO-to-H2 conversion factor. However, the
combination of this information and the ISM mass estimated from the dust mass
suggests that the ISM/gas content of XID2028 is significantly lower than
expected for its observed M$_\star$, sSFR and redshift, based on the most
up-to-date calibrations (with gas fraction <20% and depletion time scale <340
Myr). Overall, the constraints we obtain from the far infrared and millimeter
data suggest that we are observing QSO feedback able to remove the gas from the
host
