The phrase "freeing up" means to liberate or make something available. Its antonyms could include words such as restricting, limiting, blocking, or hindering. These words describe the opposite action of "freeing up," indicating that something is being held back or constrained rather than set free. For example, putting a cap on spending is a way of restricting the budget and not freeing up money for other uses. Whether it's a matter of time, resources, or personal freedom, the opposite of "freeing up" generally involves some form of constraint or obstruction, rather than opening up space or opportunity.