Incorporating atomically dispersed metal species into functionalized metal–organic frameworks (MOFs) can integrate their respective merits for catalysis. A cage‐controlled encapsulation and reduction strategy is used to fabricate single Ru atoms and triatomic Ru3 clusters anchored on ZIF‐8 (Ru1@ZIF‐8, Ru3@ZIF‐8). The highly efficient and selective catalysis for semi‐hydrogenation of alkyne is observed. The excellent activity derives from high atom‐efficiency of atomically dispersed Ru active sites and hydrogen enrichment by the ZIF‐8 shell. Meanwhile, ZIF‐8 shell serves as a novel molecular sieve for olefins to achieve absolute regioselectivity of catalyzing terminal alkynes but not internal alkynes. Moreover, the size‐dependent performance between Ru3@ZIF‐8 and Ru1@ZIF‐8 is detected in experiment and understood by quantum‐chemical calculations, demonstrating a new and promising approach to optimize catalysts by controlling the number of atoms.

With the continuous development of N-heterocyclic carbene (NHC) chemistry during the past decade, NHC metal complexes have gained wide applications in the research field of organometallic catalysis. The recycling and reuse of NHC metal complexes, which have undergone continuous expansion and diversification, can enhance their catalytic performance, extend their range of application, and afford new routes to green chemistry. Taking NHC metal complex catalysts as the main topic, this review intends to present a comprehensive study of recycling strategies of organometallic catalysts. By an elaborative summarization and classification of recycling strategies, a clear picture of all available of recycling strategies for organometallic catalysts is presented and the advantages and disadvantages of various recycling strategies for specific reactions are discussed in detail. This review is written with the hope of serving as a modest spur to induce other scientists' further contributions in the fields of catalyst recycling and sustainable catalysis.