▎ 摘　　要

NOVELTY - Preparing 2,3-butanediol (II) from ethanol, comprises adding or not adding solvent into reactor, adding ethanol (I), semiconductor photocatalyst and metal salt additive, replacing the atmosphere in the reaction system with an inert atmosphere, reacting with light, and purifying to obtain final product. USE - The method is useful in preparing 2,3-butanediol from ethanol. ADVANTAGE - The method: improves the selectivity of 2,3-butanediol and the conversion rate of ethanol through metal salt additives; utilizes cheap and easily available raw materials; and has high atom economy, excellent reaction selectivity and mild reaction conditions. DETAILED DESCRIPTION - Preparing 2,3-butanediol of formula (II) from ethanol, comprises adding or not adding solvent into reactor, adding ethanol of formula (I), semiconductor photocatalyst and metal salt additive, replacing the atmosphere in the reaction system with an inert atmosphere, reacting with light, and purifying to obtain final product; where the semiconductor photocatalyst includes semiconductor carrier and co-catalyst, the co-catalyst is loaded on semiconductor carrier, and the co-catalyst includes gold, silver, copper, iron, palladium, platinum, nickel, ruthenium, rhodium, iridium, cadmium, indium, bismuth, nickel phosphide, cobalt(II) phosphide, molybdenum disulfide, tungsten disulfide, copper(II) sulfide, graphene, and/or cobalt sulfide, the mass ratio between co-catalyst and semiconductor carrier is 0.001-0.2, preferably 0.01-0.1, and the metal salt additives include metal organic salts and metal inorganic salts of lithium, sodium, potassium, calcium, strontium, barium, aluminum, gallium, indium, vanadium, chromium, niobium, molybdenum, tungsten, manganese, iron, cobalt, copper, zinc, lanthanum, cerium, and/or praseodymium.