From 1788 Moldenhawer was the chief librarian of the
Royal Danish Library. His main interest was to increase the library's collection of recent scientific literature. Under the management of Moldenhawer, the library's book collection reached 250 000 volumes, and on Moldenhawer's death the library acquired a part of his 12,000 volume private library. Moldenhawer received numerous honors for his work. In 1809 he became a
Knight of the royal Danish Order of the Dannebrog. Besides administrative talents Moldenhawer was also an author. He brought from his travels numerous excerpts and collations, including political history, church and literary history, theology and oriental philology. He was always heavily occupied with his work and duties, especially library work, which was his favorite duty. At auction for the printed books he bought over 50,000 volumes for 10,000
thalers from the former private collection of
Otto Thott (1703–1785). 6159 books of this collection were printed before 1530. He made a second major acquisition in 1796 when he acquired the book collection of
Peter Frederik Suhm. Moldenhawer purchased this collection on the condition that the payment would continue in the form of an annuity for Suhm and his wife, but both died shortly after the purchase was completed. In 1797 he purchased the collection of Müllerske Pinakothek (with annual payments to the collector's daughter). == Allegations by Ada Adler ==