Metal-organic frameworks bonded with metal N-heterocyclic carbenes for efficient catalysis

Metal N-heterocyclic carbenes (M-NHCs) on the pore walls of a porous metal-organic framework (MOF) can be used as active sites for efficient organic catalysis. Traditional approaches that need strong alkaline reagents or insoluble Ag2O are not, however, suitable for the incorporation of NHCs on the backbones of MOFs because such reagents could destroy their frameworks or result in low reactivity. Accordingly, development of facile strategies toward functional MOFs with covalently bound M-NHCs for catalysis is needed. Herein, we describe the development of a general and facile approach to preparing MOFs with covalently linked active M-NHC (M = Pd, Ir) single-site catalysts by using a soluble Ag salt AgOC(CF3)(3) as the source and subsequent transmetalation. The well-defined M-NHC-MOF (M = Pd, Ir) catalysts obtained in this way have shown excellent catalytic activity and stability in Suzuki reactions and hydrogen transfer reactions. This provides a general and facile strategy for anchoring functional M-NHC single-site catalysts onto functionalized MOFs for different reactions.