CHAMPAIGN—For one half Sunday, Purdue’s shooting was brutal.Airballs fell silently short. Balls that did find the rim clanked harmlessly off.The shooting was so bad — 28.6 percent — that after one errant miss by JaJuan Johnson, Purdue coach Matt Painter eyed his leading scorer with exasperation as Johnson ran back upcourt, the coach’s arms stretched wide and his hands raised as if to say, “What was that?” But the No. 14 Boilermakers said their coach made just one calm request after the first half: Come out hard in the second. They did, blasting the Illini with 54 second-half points, outrebounding them 28-9 over that stretch and locking up a comeback 81-70 win.The Illini (16-9, 6-6 Big Ten) led or were tied for all but 1:17 of the first half and went to the locker room up 32-27. But they knew, coach Bruce Weber said, that a storm was coming.The result keeps the Boilermakers (20-5, 9-3) two games back and within reach of first-place Ohio State. The Illini, meanwhile, drop back to the middle of the Big Ten pack, and — just three days after a big road win at Minnesota — were left pointing fingers over who was to blame.The Boilermakers started their second-half push with a 10-4 run that gave them just their second lead of the afternoon. And they made it stick.E’Twaun Moore, who finished with 20 points, hit a 3-pointer with 16:05 to play that put Purdue up 37-36.Mike Davis made a pair of free throws with 12:48 left to cut Purdue’s lead to 45-44. But Terone Johnson hit a 3-pointer 23 seconds later, and Ryne Smith followed that with a layup that made the score 50-44.A minute later, with Illinois back to within 50-46, Smith and point guard Lewis Jackson combined for what might have been the offensive play of the game, and one that took the life out of the Illini crowd.Jackson dribbled across the lane and spotted Smith open near the top of the key. Smith hit a 3-pointer for a 53-46 lead. Illinois was led by Brandon Paul’s 23 points. D.J. Richardson finished with 13. Demetri McCamey returned to the starting lineup after playing off the bench against Minnesota, but finished with just 4 points, 10.8 below his average.