import pandas as pd

df1 = pd.DataFrame({'A': [1, 2, 3, 4], 'B': ['a', 'b', 'c', 'd']})
df2 = pd.DataFrame({'A': [2, 4], 'B': ['b', 'd']})

merged_df = pd.merge(df1, df2, how='outer', indicator=True)
filtered_df = merged_df[merged_df['_merge'] == 'left_only'].drop('_merge', axis=1)
print(filtered_df)