He was a recipient of the Kossuth Prize, a member of the Hungarian Academy of Sciences, and was the brother of Professor Győző Zemplén.

His major field of research was structural chemistry and biochemistry including the synthesis of naturally occurring flavonoid-glycosides (isolated from plants).

On the invitation of Emil Abderhalden, an eminent biochemist, Zemplén participated in the writing of Biochemisches Hand-lexikon and also Handbuch der biochemischen Arbeitsmethoden.

In 1932 Dr. Zemplén received the Corvin chain (a national award founded in remembrance of King Mátyás Hunyadi) in recognition of his activity abroad as well as in Hungary.

[4] Between 1930 and 1940 Zemplén continued research on the naturally occurring flavonoid-glycosides and succeeded in elucidating the structures of several of them, as well as accomplishing their total syntheses.

During the course of World War II he continued his research although his institute was almost entirely ruined due to the Siege of Budapest.

Professor Zemplén is the author of more than 200 scientific publications and a textbook entitled Szerveskémia ("Organic Chemistry").

In the Handbuch der biochemischen Arbeitsmethoden (1912-1913), Zemplén wrote about the production and detection of glucosides as well as other, higher carbohydrates.