If want filter columns names with 0 or 1 values:

c = df.columns[df.isin([0,1]).all()]
print (c)
Index(['col', 'col2'], dtype='object')

If need filter columns:

df1 = df.loc[:, df.isin([0,1]).all()]
print (df1)
   col  col2
0    0     1
1    0     0
2    0     0
3    0     0
4    0     1