Let me explain how Passive PoE works.
Passive PoE is indeed a possibility to power the router over LAN1 port, but there are some requirements that you must meet to make it work.
First of all, you must understand that Passive PoE is a way to send electric current out over the Ethernet cable at a certain voltage regardless of the device it's going to. It means that there is no negotiation between the power you're sending through it and a device itself.
Second of all, unlike Passive PoE, there is Active PoE which negotiates the right amount of voltage between the switch and PoE-powered devices. So you must never forget the difference between them and make research before connecting anything that sends electric current to your LAN port.
What you should also have in mind, that there are power supply standards and the device is NOT COMPLIANT with the IEEE 802.3af-2003 and IEEE 802.3at standards as they will damage the router. You can find more information about it here: https://wiki.teltonika-networks.com/view/TRB140_Powering_Options
To make Passive PoE work you will need something to negotiate between the power and a router, it could be passive PoE injector or Active to Passive PoE converter. Supply voltage must be in the 9-30 VDC range.
I hope this was helpful.