Clockspeed isn't the only measure of how a CPU performs. Pentium 4 is an extremely outdated CPU that had an architecture notorious for getting little work done each clock cycle. The Core i3 has a much newer architecture that gets more than double the amount of work done each clock cycle compared to the Pentium 4. The i3 is also a dual core CPU with hyperthreading, while the 2.2GHz Pentium 4 is a single core CPU.
Just because the Pentium 4 is clocked higher, does not make it a better CPU than even an ultra low voltage model i3. Despite the i3's lower clock speed, it is much faster than the Pentium 4 due to a more efficient architecture, having 2 cores rather than 1, and also having hyperthreading.