The only goal of the game came in the sixth minute when Jong In-hwan was adjudged to have tripped Adrian Chuva in the area and fellow Brazilian Mota stepped up to stroke the penalty past Kwon Jung-hyuk.
"This was our toughest game of the season," said Pohang coach Hwang Sun-hong.
"Our players had a very strong desire to keep a clean sheet and I appreciate that.
"The win is important if we want to keep the pressure on at the top of the table. There are still five games remaining and we will see what happens."
Ulsan Horangi kept their play-off hopes alive with a 3-1 win at home to struggling Sangju Sangmu.
Lee Jin-ho put the hosts in front after 30 minutes but Sangju were back on level terms just before the hour mark thanks to Lee Sung-jae's strike.
With 20 minutes remaining, Kwak Tae-hwi restored Ulsan's lead and Park Sung-il then sealed the win shortly afterwards.
Elsewhere, Seongnam crashed to a 3-1 home defeat at the hands of Gwangju FC. Lee Sung-ki put the visitors ahead after just three minutes and Kim Dong-sub made it two just before the break.
Dzenan Radoncic pulled a goal back for Seongnam, who saw Sasa Ognenovski sent off with 20 minutes remaining, but Joao Paulo sealed the points in the final minute.
Finally, Daegu FC and Daejeon Citizen drew 2-2. Kim Sung-joon and Park Sang-ho got the goals for Daejeon while Song Jae-hon netted twice for Daegu.