Can different functionalized silicas be mixed?

Yes, if you don’t need them to interact together. One of the key benefits of using supported reagents and scavengers is that you can mix incompatible functional groups such as acids and bases together and they won’t interact with each other.

This is due to two reasons, the relative size of the functional group is very small compared to the size of the particle to which it is attached (roughly 100 000 orders of magnitude difference) and, at least 95% of the moieties are grafted inside the pore structure.

For some reactions, such as amide coupling with Carbodiimide and HOBt, you need the reagents to interact so only one of them can be supported.