Which enzyme is responsible for facilitating the hydrogen bonding between nucleotides in a new dna molecule ?

The enzyme DNA polymerase is responsible for linking the nucleotides in a new DNA strand.

Before replication of DNA occurs, the DNA double helix is first unwound, after which the two strands must be separated  much like the two sides of a zipper by breaking the weak hydrogen bonds that link the paired bases.

The unwound DNA strands are held apart to expose the bases so that new nucleotide partner can hydrogen-bond to them. It is DNA polymerase that moves along the exposed strand, joining newly arrived nucleotides  into a new DNA strand  by linking paired  bases by hydrogen bonds.