concatenate dataframe awith different order of column

Question

I have two dataframes : df1:

    Cluster OsId    BrowserId   PageId  VolumePred  ConversionPred


 0 11   11  {789615, 955761, 1149586, 955764, 955767, 1187...   147.0   71.0
 0 11   12  {1184903, 955761, 1149586, 1158132, 955764, 10...   73.0    38.0
 0 11   15  {1184903, 1109643, 955761, 955764, 1074581, 95...   72.0    40.0

and df2

   Cluster  OsId    PageId  BrowserId   VolumePred  ConversionPred
    0   11  789615  {16, 17, 11}    163.0   80.0
    0   11  835198  {16}    37.0    21.0
    0   11  858236  {16}    4.0 3.0

And I need to concatenate them to get this result:

Cluster OsId    BrowserId   PageId  VolumePred  ConversionPred
    0    11     11         {789615, 955761, 1149586, 955764, 955767, 1187...    147.0   71.0
    0    11     12         {1184903, 955761, 1149586, 1158132, 955764, 10...    73.0    38.0
    0    11     15         {1184903, 1109643, 955761, 955764, 1074581, 95...    72.0    40.0
    0   11  {16, 17, 11}   789615                                               163.0   80.0
    0   11  {16}           835198                                                37.0   21.0
    0   11  {16}           858236                                                 4.0   3.0

I try with simply this line of code :

result = pd.concat(df1,df2)

But I got this error :

TypeError: first argument must be an iterable of pandas objects, you passed an object of type "DataFrame"

An idea please to help me to fix it

print(df1)
> Cluster  OsId  BrowserId  \ 0        0    11         11    1        0 
> 11         12    2        0    11         15   
> 
>                                               PageId  VolumePred  \ 0  {789615, 955761, 1149586, 955764, 955767, 1187...       147.0    1 
> {1184903, 955761, 1149586, 1158132, 955764, 10...        73.0    2 
> {1184903, 1109643, 955761, 955764, 1074581, 95...        72.0   
> 
>    ConversionPred   0            71.0   1            38.0   2         
> 40.0

Thanks you!