Increasing working temperature span in Ni-Mn-Sn-Co alloys via introducing pores

•Ni40.7Mn42.9Sn10.4Co6.0 foam with porosity 56% was created by replication casting and annealing.•The foam had reduced thermal hysteresis (9.0 K).•The foam showed entropy change 4.7 J/kg·K with working temperature span 40 K under 5.0 T.•The foam exhibited a small hysteresis loss (AHL) 17.4 J/kg under 5.0 T.•The foam produced refrigeration capacity 155 J/kg and relative cooling power 188 J/kg.