Is it permissible to accept a sum of money from a contractor in exchange for recommending him for projects under construction and contributing to the awarding of contracts to him?

It is not permissible to take money from contracting companies in exchange for nominating them if the nomination is part of your job, because it falls under the category of forbidden gifts to employees. However, if it is outside the scope of your work, then it is permissible to take money, provided that it is free from uncertainty (gharar), deception, misrepresentation, and anything that harms the sector.