In 1085 or 1092, he wrote a treatise on the practice of charistikion, whereby the emperor could grant a monastery to a private person for a specified period.
[1] At the time of the Siege of Antioch in 1097 by the Christian armies of the First Crusade, he was imprisoned by the Seljuk governor Yağısıyan, who suspected his loyalty.
According to the Historia belli sacri (c. 1131), after the siege the Christian women of the city went to release the imprisoned patriarch, only to find that he could not stand, his legs having been weakened by so long a confinement.
Bohemond accused him of conspiring with Byzantine emperor Alexios I, and John was exiled to Constantinople.
John made enemies among the monks of his new home and was forced to leave the Hodegon for the island of Oxeia in the Sea of Marmara, where he was eventually buried.