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Direct synthesis of 2,1-benzisoxazole and its related N-heterocyclic compounds via a chemoselective reductive heterocyclization route, which involves hydrogenation and subsequent intramolecular cyclodehydration steps, is a viable and attractive approach. However, the efficient transformation of the feedstocks using hydrogen as a hydrogen source at ambient temperature and atmospheric hydrogen pressure remains a great challenge. Herein, we reported a MgO-incorporated porous carbon composite (MgO@C) stabilized subnanometric Pt cluster (Pt/MgO@C) catalyst prepared by annealing a Mg-containing metal–organic framework, Mg-MOF-74, followed by impregnation of a Pt precursor and further reduction treatment strategy. The as-prepared Pt/MgO@C with ultralow Pt loading (0.078 wt%) exhibited superior catalytic performance for synthesizing 2,1-benzisoxazole derivatives by the reductive heterocyclization methodology. Excellent catalytic activity (conversion ≥ 99%), high chemoselectivity (≥92%), good stability (8 cycles), and broad functional group tolerance (10 substrates) were achieved under very mild conditions (1 bar hydrogen pressure at 303 K) over the developed Pt/MgO@C. Control experiments indicated that a proper amount of basic sites, subnanometric Pt clusters, and a close contact between them synergistically contributed to the extraordinary performance of Pt/MgO@C. Density functional theory calculations showed that the high activity and chemoselectivity of Pt/MgO@C stemmed from the active interfacial sites of Pt/MgO@C simultaneously activating the H2 and substrate, where the formed stable hydroxyl groups contributed to the enhancement of activity. The combined experimental and theoretical approach identified the formation of the –NO and –NHOH groups during the hydrogenation process, and the former corresponds to the rate-determining step. [ABSTRACT FROM AUTHOR]

MOF-74-type frameworks are considered one of the most promising metal–organic frameworks owing to their remarkable structural features and properties such as a high density of open metal sites, hexagonal channels along the c-axis, and high porosity. Diverse strategies have been adopted to prepare bimetallic MOF-74 frameworks, in the pursuit of synergistic effects and enhanced properties originating from different metal sites that serve as Lewis acidic sites. Moreover, extended versions of the MOF-74-type structure have been demonstrated in terms of ligand extension, featuring enhanced pore size and surface area. The extended variants of MOF-74 are beneficial for the incorporation of additional functional groups due to the relatively larger pore size. Pre- or post-synthetic modification approaches have been applied to introduce functionalities into the framework, resulting in desirable and superior properties such as chemical stability, binding affinity, and catalytic activity. This review addresses the significant progress made in the development of MOF-74-type frameworks with respect to synthetic strategies and modification approaches. [ABSTRACT FROM AUTHOR]

A porous Zr metal–organic framework, 1-PdBF4 [Zr6O4(OH)4(OAc)2.4{(PNNNP)Pd(MeCN)}2.4(BF4)2.4; PNNNP = 2,6-(HNPAr2)2C5H3N; Ar = p-C6H4CO2−], has been synthesized via postsynthetic oxidative I−/BF4− ligand exchange using NOBF4. 1-PdBF4 enjoys markedly superior catalytic activity and recyclability to its trifluoracetate-exchanged analogue, 1-PdTFA, for the intramolecular cyclization of o-alkynyl anilines and the carbonyl–ene cyclization of citronellal. Moreover, 1-PdBF4 demonstrates a rare example of pore selective catalysis for the cyclization of 2-ethynyl aniline. [ABSTRACT FROM AUTHOR]

Molecular trimeric ruthenium carboxylate clusters (Ru3 clusters) have been introduced into the pore channels of mesoporous metal–organic framework chromium terephthalate [MIL-101(Cr)] by employing a facile two-step post-synthetic strategy in which diamine hooks anchored on the framework metal nodes of the MOF are used to covalently immobilize the Ru3 clusters. The catalytic activity of the isolated Ru3 clusters in the pore channels of the MOF was significantly improved compared to the bulk counterpart. [ABSTRACT FROM AUTHOR]