We report a one-step synthetic strategy to encapsulate copper nanocrystals (Cu NCs) in a carboxylate-based metal organic framework (MOF-74) to construct Cu@Cu-MOF-74 hybrids. One of the hurdles to realizing metal NC@MOF hybrids with uniform morphology and with a homogeneous NC spatial distribution by chemical transformation is to precisely match the metal dissolution rate and the MOF crystallization rate. Our study defines the parameter space which controls this kinetic balance. Such an understanding and the generality of our approach is crucial to develop rules of design for NC@MOF hybrids, which represent an attractive class of materials for several applications.