Eric Ming scored the lone goal for the Rangers, who were outscored 16-11 in the series.
John Gibson stopped 29-of-32 shots in defeat.
Maatta scored on the power play 7:15 into the first period to put the Knights ahead 1-0 after 20 minutes of play.
Tierney doubled London's lead early in the second period and Rupert added another power-play goal at 15:42.
Ming scored late in the second to put Kitchener on the board, however Domi scored into an empty net at 19:02 of the third period to secure a London victory.
The Knights went 2 for 7 on the power play while the Rangers failed to score on four chances with the man advantage.
London will face either the Plymouth Whalers or Owen Sound Attack in Round 3. Plymouth leads the series 3-2 with Game 6 set for Sunday in Owen Sound.