Competent production of hydrogen and hydrogenation of carboxylic acids using urea-rich waste water over visible-light-responsive rare earth doped photocatalyst

Background: A strategy employing water as a hydrogen source is promising but challenging. Conversely, urea is the major pollutants causing substantial water pollution. Moreover, direct reduction of carboxylic acids into aldehydes is still a great challenge due to higher propensity of aldehydes being further reduced to alcohols.Methods: We report a visible-light driven one-step protocol to selectively convert aromatic carboxylic acids to aldehydes with water as the sustainable hydrogen source, environmental pollutant urea as a hole scavenger and Eu3+ doped Na2CaP2O7 phosphor as a viable photocatalyst. Significant findings: Apart from the photocatalytic H2 evolution, the procedure is able to reduce a broad range of carboxylic substrates with good functional group tolerance in good to excellent yield. The insertion of Eu3+ into the present host creates several metastable states inside the forbidden region and thereby led to enhancement of photo stimulation process. Moreover, various experiments and analytical analysis reveal that photo-generated active H-species from water are the direct reducing agent, skipping the use of traditional flammable H2. Pre-sent work provides a 'waste-to-value' route for solar energy driven preparation of valuable chemicals by simultaneous photocatalytic treatment of urea-rich waste water.