Primary alkyl alcohols can be directly converted into acetals and H₂via TiO₂-photocatalytic dehydrogenation coupling at room temperature, with no need for any hydrogen acceptors. The reaction follows a tandem process integrating photocatalytic alcohol dehydrogenation and H⁺-catalytic acetalation, in which the H⁺ ion catalysts are provided by the alcohol dehydrogenation in real time. This approach exhibits a very high reaction rate and product selectivity, and represents a novel green process for the conversion of primary alkyl alcohols, especially for bio-renewable ethanol and 1-butanol.