Is it permissible to convert my pension to a fixed interest system at 100% and donate its proceeds, especially since the current stock investment system does not deal in prohibited matters?

Usury is forbidden by Islamic law and has dire consequences in this world and the Hereafter. Engaging in prohibited contracts such as usury and gambling is not permissible, even with the intention of donating whatever is earned from them; the sin is inherent for anyone who engages in them. Indeed, the Prophet Muhammad, peace and blessings be upon him, cursed the one who consumes usury, the one who feeds it, its scribe, and its two witnesses, for they are all equal in sin. One who engages in these prohibited transactions does not benefit from giving charity with such funds; they are like impurities that must be disposed of, and Allah is good and accepts only what is good. Furthermore, the Permanent Committee for Scholarly Research and Ifta has issued a fatwa stating that it is not permissible to deposit money in usurious banks with the intention of taking usurious interest for any purpose whatsoever, because it is unlawful and vile gain.