Exhaust after-treatment systems and methods are disclosed. An example system includes a selective catalytic reduction on filter (SCRF) and a selective catalytic reduction (SCR) catalyst positioned downstream of the SCRF. The system also includes a first reductant doser positioned upstream of the SCRF and a second reductant doser positioned downstream of the SCRF and upstream of the SCR catalyst. The system further includes first and second nitrogen oxide (NOx) sensors positioned upstream of the first reductant doser, a third NOx sensor positioned downstream of the SCRF and upstream of the second reductant doser, and a catalyst positioned upstream of the first reductant doser.