Question

how is the frequency of a pendulum affected if its taken to vacuum

Answer 1

As many of the other answers say, it will go on
swinging forever, provided that there are no
friction losses or magnetic or electrical
interferences.
It doesnt mean that you can extract infinite
energy out of the pendulum. The pendulum has
a fixed amount of energy. All that is happening
is the energy getting converted from potential
energy to kinetic energy during the oscillation of
the pendulum, Once you start extracting energy,
the pendulum slows down, and ultimately stops.
Sorry to tell you this, but almost all those
'infinite energy' ideas have logical loopholes in
them.. I havent come across a really good one
yet......