Quicken accounting software 2015 for Mac doesn't export QIF files. However, it does export QMTF files easily, which are actually very similar to QIF files with a diverse extension. You can export your data from Quicken 2015 for Mac into a QMTF file and then rename the QIF file extension to import it. The only catch was that there was no good way to get data directly from Quicken Essentials to iBank. The CSV export-import method produced a mess when I imported them. I did, however, discover that the Mac version of Moneydance (another Mac finance software) has the ability to import directly from the Quicken Essentials data file.
QXF is a proprietor binary format and only Quicken Inc knows the format. You might try this method (but only if you can get on a Windows machine) that is being used to convert to Quicken Windows. Note you can't include any investment accounts with this procedure. Also note the document was written for Quicken Essentials so keep that in mind when you use it for Quicken 2016 Mac.
If it isn't possible to get a Windows machine it might be possible to find some CSV to QIF converter for Mac that will do the same job. But in fact I doubt it, since it isn't a simple 'transactions convert', it has to put in information for accounts and such.