Using macbook charger to iphone 14 pro max

Yes, it is both possible and safe. Also see the following from Fast charge your iPhone - Apple Support

(Note that the 70 watt model isn't specifically listed as it was released later, but it can be used like the other ones listed.)

To fast charge, you need an iPhone 15 model with a USB-C cable like the one that came in the box or an earlier iPhone model with a USB-C to Lightning cable and one of these adapters:

• Apple 18W,* 20W, 29W, 30W, 35W, 61W, 67W, 87W, or 96W, or 140W USB-C Power Adapter
• A comparable third-party USB-C power adapter that supports USB Power Delivery (USB-PD)

The iPhone 14 Pro Max is included in the "or an earlier iPhone model with a USB-C to Lightning cable" statement in that article.