#"Photosynthesis"# produces simple sugars, and as a bonus, dioxygen, from carbon dioxide, and water, in the presence of sunlight....and we can represent this reaction by the equation....
#6CO_2(g) + 6H_2O(l) stackrel(hnu)rarrC_6H_12O_6(aq) + 6O_2(g)#
Because we BREAK strong #C=O# and #H-O# bonds, substantial energy input must be made to the reaction, and this is supplied by solar energy... And so can you tell us why photosynthesis does not occur at night-time....?