Mohamed Hany’s 53rd-minute strike saw off the Mexican side at the Al Nahyan Stadium in Abu Dhabi.
Al Ahly, without several Egypt players who are on duty at the Africa Cup of Nations, will face Brazilian team Palmeiras on Tuesday at 16:30 GMT.
Chelsea will discover their last-four opponents on Sunday when Saudi Arabia’s Al Hilal face hosts Al Jazira.
Chelsea play on Wednesday, with the final scheduled for 12 February.
The Blues, who beat Plymouth in the FA Cup fourth round on Saturday, will fly out without boss Thomas Tuchel after the German tested positive for coronavirus.
The Club World Cup features the winners of the continental cups in Fifa’s six confederations and the league champions from the United Arab Emirates.
The tournament was due to be played in Japan in December but was postponed and moved to the UAE.
However, the revised dates clashed with the culmination of the Nations Cup in Cameroon, where Egypt play Senegal in the final on Sunday at 19:00.
