I just bought a Belkin 108W GaN USB Charging Station at the Apple store, I was told it would charge my 16" 2021 Macbook pro. The charger that came with the Macbook pro is 140 W. Will it work without causing damage to my Mac?

See:

Identify your Mac power adapter - Apple Support - "If your Mac uses USB-C to charge, you can charge your Mac laptop with

any USB-C power adapter or display. You can safely use a power adapter

or display with higher or lower wattage than the adapter included with

your Mac. For the best charging experience, you should use the power

adapter and cable included with your MacBook Air, MacBook Pro, or MacBook."

Any external power supply that provides "USB Power Delivery" (including certain displays) must negotiate over the USB cable using USB Power Delivery Protocol, and can not 'force itself' on your Mac. The Voltage and Current are delivered only after your Mac requests and the charger agrees to supply power under certain controlled conditions. The computer is in control of the entire process.

That charger can supply the maximum possible across a 100W rated USB-C cable, which is great for regular charging your 16-in MacBook Pro.

Fast charging your 16-in MacBook Pro requires the MagSafe connection, and can use up to the 140 Watts your Apple power adapter can supply over MagSafe.

You can use a compatible higher wattage adapter without issue, but it won't make your computer charge faster or operate differently. Lower wattage adapters will not provide enough power during normal computer use. They may charge if the computer is not in use, but it will be slower.