Apparently it's been planned since 2012. From Reporterre (in French)

Although construction has begun, the project was not conceived by the Brazilian government for the event. The Extraordinary Secretariat for COP30 issued a press release on 13 March, stating that the project "does not fall under the responsibility of the federal government [Brazil's central state] and is not one of the 33 infrastructure projects planned for COP30". It deplored the fact that press articles had "wrongly suggested a link between the construction project and the federal government's actions in the run-up to the conference".

Translated with DeepL