Bromine gas can also be reactively absorbed by alkali aqueous solutions of NaOH or KOH; for the last: 3Br2 + 6KOH → 5KBr + KBrO3 + 3H2O. It is necessary, however, to avoid later neutralization and acidulation of the resulting solution, since bromine could possibly be released if its solubility is somehow exceeded: KBrO3 + 5KBr + 6HCl ↔ 6KCl + 3Br2 + 3H2O.

Yet another possibility, could be the reactive absorption of bromine gas by a sodium carbonate aqueous solution: 3Br2 + 3Na2CO3 → 5NaBr + NaBrO3 + 3CO2. However, acidulation of the resulting solution should be avoided, since bromine could be partially regenerated and released from the solution if its solubility is exceeded: NaBrO3 + 5NaBr + 6HCl ↔ 6NaCl + 3Br2 + 3H2O.

You have already got two suggestions from Queiroz, which appears to me to be plausible.

Bromine gas is a relatively strong oxidising agent and hence the logical requirement is a reducing agent. What about using aqueous sodium / potassium sulphite / bisulphite solution, - Na2SO3 / K2SO3 solution or NaHSO3 / KHSO3 solution. You may think of some other reducing agent as well.

There could be another way of achieving the same goal and it is passing the gas through a solution wherein the bromine reacts and as a result a precipitate is formed. This is most likely to be possible if you pass the gas through an aqueous solution of silver nitrate ( AgNO3 ) or lead nitrate [ Pb(NO3)2 ]. As usual you may think of any other compound that might give rise to precipitation.

Now, I would like to request you to spread your imagination and find out some more ways / reactions to achieve your goal. After all that is what research is.

Wish you all the best,

ARB