A zinc acetate borate, [ZnAc]·[ZnBO3] (1), was synthesized under mild conditions; the B@Zn2O3 layer of 1 contains a 6-membered ring embedded with a rare BO3 unit. The layers are pillared by acetate ions to form a 3D framework. The pillared structure of 1 supplies enough space as a nanoreactor, and the related application of CO2-to-CO reduction has been confirmed.