numpy array: split horizontally and add dimension

Question

I have a numpy array

[
[1,2,3,4], 
[5,6,7,8], 
[9,10,11,12]
]

Now I want to split them into

[
[[1,2],[3,4]],
[[5,6],[7,8]],
[[9,10],[11,12]]
]

How can I achieve this?

Thanks for helping! Regards.