A General Strategy to Immobilize Single-Atom Catalysts in Metal-Organic Frameworks for Enhanced Photocatalysis

Single-atom catalysts (SACs) are witnessing rapid development due to their high activity and selectivity toward diverse reactions. However, it remains a grand challenge in the general synthesis of SACs, particularly featuring an identical chemical microenvironment and on the same support. Herein, a universal synthetic protocol is developed to immobilize SACs in metal-organic frameworks (MOFs). Significantly, by means of SnO2 as a mediator or adaptor, not only different single-atom metal sites, such as Pt, Cu, and Ni, etc., can be installed, but also the MOF supports can be changed (for example, UiO-66-NH2, PCN-222, and DUT-67) to afford M-1/SnO2/MOF architecture. Taking UiO-66-NH2 as a representative, the Pt-1/SnO2/MOF exhibits approximately five times higher activity toward photocatalytic H-2 production than the corresponding Pt nanoparticles (approximate to 2.5 nm) stabilized by SnO2/UiO-66-NH2. Remarkably, despite featuring identical parameters in the chemical microenvironment and support in M-1/SnO2/UiO-66-NH2, the Pt-1 catalyst possesses a hydrogen evolution rate of 2167 mu mol g(-1) h(-1), superior to the Cu-1 and Ni-1 counterparts, which is attributed to the differentiated hydrogen binding free energies, as supported by density-functional theory (DFT) calculations. This is thought to be the first report on a universal approach toward the stabilization of SACs with identical chemical microenvironment on an identical support.