A strong start fizzled into a disappointing defeat in Minnesota.
The Nittany Lions have now won 20 of the past 21 matches against the Spartans.
Penn State women's hockey is still standing as the only undefeated team in the nation.
Franklin's five-year deal is worth $41.75 million.
Cook had a .554 winning percentage in eight years at Penn State.
Nebraska will lean on freshman quarterback TJ Lateef after Dylan Raiola went down with an injury.