You got the error because Batch operations are not supported with Mainframe. Only supported methods are PutFile, GetFile and GetList.

You can write your own PutFiles method for example like this:

private static void PutFiles(Ftp client, string localPath, string fileMask, string remotePath)
{
    if (string.IsNullOrEmpty(fileMask))
        fileMask = "*";

    string[] localFiles = Directory.GetFiles(localPath, fileMask);
    foreach (string localFile in localFiles)
    {
        string name = Path.GetFileName(localFile);
        string remoteFile = RemotePathCombine(remotePath, name);
        client.PutFile(localFile, remoteFile);
    }

    string[] localDirectories = Directory.GetDirectories(localPath);
    foreach (string localDirectory in localDirectories)
    {
        string name = Path.GetFileName(localDirectory);
        string remoteDirectory = RemotePathCombine(remotePath, name);
        PutFiles(client, localDirectory, fileMask, remoteDirectory);
    }
}

private static string RemotePathCombine(string remotePath, string name)
{
    return string.Format("{0}/{1}", remotePath.TrimEnd('/'), name);
}

You can use it like this:

Ftp client = new Ftp();
client.Connect(ftpServerIP);
client.Login(ftpUserID, ftpPassword);
client.TransferType = FtpTransferType.Ascii;

PutFiles(client, @"c:\test", "*.xml", "//HRUNT.PER.ED.DE34.ACK.DDATA(+1)");

Please note the method RemotePathCombine. You have to write your own implementation of it according to your Mainframe. Given implementation is for common FTP server.