Is the capital recuperated from the bank after taking its interests and donating them to the poor considered unlawful (haram), and is this action lawful (halal) or unlawful (haram)?

It is not permissible to deposit money in a usurious bank, even if the depositor disposes of its interest, because it constitutes assistance in usury. This is only allowed in cases of necessity, assessed proportionately, such as protecting money from damage or theft when no Sharia (definition)-compliant alternative exists. If the necessity ceases, the money must be withdrawn. The principal amount recovered is lawful due to its origin. The interest must be disposed of by spending it on general Muslim welfare or giving it to the poor. One does not receive the reward of charity for it.