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Graphical abstract Highlights • A robust heterogeneous catalyst derived from Zn/Co-ZIF is explored for the CO 2 conversion. • A fast production of the Zn/Co-ZIF template with high crystallinity was achieved via spray drying. • Excellent dispersion of the metal in the N-doped carbon matrix was demonstrated. • The metal and the N-sites in the carbon matrix act as catalytic sites. • The magnetic properties of the catalyst allowed easy separation and recycling. Abstract A robust catalyst generated from the pyrolysis of bimetallic Zn/Co-ZIF comprising magnetic properties demonstrated to be an effective heterogeneous catalyst system for CO 2 conversion reaction without the need of co-catalyst and solvent. Controllable pyrolysis under various conditions resulted in a unique active structure composed of metallic particles stabilized in a nitrogen-doped carbon matrix. The metallic particles acting as acid sites are dispersed in a nitrogen-doped porous carbon-wall which provides the basic sites. These sites are created during the pyrolysis process of Zn/Co-ZIF used as a special template under a controlled atmosphere. The resulting material possessing both, acid and basic sites, showed an excellent catalytic performance for the cycloaddition of CO 2 into epoxides as these sites correspond to the active sites in the catalytic cycle. Additional, the pyrolysis conditions indicated to play an important role in the properties of the resulting materials and in parallel with the catalytic performance. The catalytic material proved to be very robust and maintained high activities for at least eleven cycles using the optimized reaction condition. Moreover, the magnetic property of the resulting catalyst is advantageous especially for the separation from the reaction mixture. [ABSTRACT FROM AUTHOR]

The catalytic activity of ZIF-8 in the ring-opening polymerization of l-lactide without solvents or cocatalysts is presented for the first time. Two different synthetic strategies have been applied for synthesizing ZIF-8, either under solvothermal condition or by spray-drying procedure. Their catalytic activities are found to be correlating with the presence of open active sites in ZIF-8 structure. The structural defects that afford active acid and basic sites are supposed to cooperatively catalyze the reaction. ZIF-8 assembled by spray-drying technique, displays a superior catalytic activity at temperature of 160 °C, leading to the formation of high molecular weight cyclic polylactide. The ZIF-8 catalysts could be recycled and reused without any significant loss of catalytic activity. [ABSTRACT FROM AUTHOR]

A series of high-quality M2(BDC)2(DABCO) metal-organic frameworks (abbreviated as M-DABCO; M=Zn, Co, Ni, Cu; BDC=1,4-benzene dicarboxylate; DABCO=1,4-diazabicyclo[2.2.2]octane), were synthesized by using a solvothermal (SV) method, and their catalytic activity for the cycloaddition of CO2 to epoxides in the absence of a co-catalyst or solvent was demonstrated. Of these metal-organic frameworks (MOFs), Zn-DABCO exhibited very high activity and nearly complete selectivity under moderate reaction conditions. The other members of this MOF series (Co-DABCO, Ni-DABCO, and Cu-DABCO) displayed lower activity in the given sequence. Samples of Zn-DABCO, Co-DABCO, and Ni-DABCO were recycled at least three times without a noticeable loss in catalytic activity. The reaction mechanism can be attributed to structural defects along with the acid-base bifunctional characteristics of these MOFs. Moreover, we illustrate that the synthetic method of M-DABCO influences the yield of the reaction. In addition to the SV method, Zn-DABCO was synthesized by using spray drying due to its industrial attractiveness. It was found that the synthesis procedure clearly influenced the crystal growth and thus the physicochemical properties, such as surface area, pore volume, and gas adsorption, which in turn affected the catalytic performance. The results clarified that although different synthetic methods can produce isostructural MOFs, the application of MOFs, especially as catalysts, strongly depends on the crystal morphology and textural properties and, therefore, on the synthesis method. [ABSTRACT FROM AUTHOR]

A series of metal organic frameworks (MOFs) MDABCO (M = Co, Ni, Cu, Zn; DABCO = 1,4-diazabicyclo[2.2.2]octane) are utilized as catalysts for the bulk ring-opening polymerization of l -lactide. The catalytic activity varies in the order CuDABCO, NiDABCO < ZnDABCO, CoDABCO. By adding lactic acid, we unexpectedly observed enhanced catalytic activity. The combined use of lactic acid and ZnDABCO during polymerization results in a highly active polymerization system, along with the gradual change of MOFs structure caused by an increased acid concentration. Compared to related homogeneous fragments, such as zinc nitrate and 1,4-diazabicyclo[2.2.2]octane, ZnDABCO is found to afford highly isotactic polylactide, which would be ascribed to the unique structural properties of MOFs. [ABSTRACT FROM AUTHOR]

The Cover Feature shows a new approach to cyclic polylactide in the bulk ring ‐ opENing polymerization (ROP) of l ‐ lactide by using ZIF ‐ 8 as a heterogENeous catalyst. The ZIF ‐ 8 catalyst assembled by spray ‐ drying technique displays high efficiENcy and good recyclability for this ROP reaction. The active acid and basic sites in ZIF ‐ 8 are supposed to cooperatively catalyze the ROP reaction, particularly forming cyclic polylactide with high molecular weight. More information can be found in the Communication by Luo et al. on page 4135 in Issue 21, 2017 (DOI: 10.1002/cssc.201701438). [ABSTRACT FROM AUTHOR]

• Assembly from core-structure UiO-66 with shell-structure UiO-67-BPY was explored. • The Lewis basic sites from the linker are advantageous for base-catalyzed reactions. • The core-shell was applied as a catalyst for the Knoevenagel condensation. • UiO-67-BPY@UiO-66 as a heterogeneous catalyst showed excellent yields. • The catalyst can be recycled maintaining its high catalytic performance. A core-shell structure metal-organic framework based on the Zr clusters bridging with BDC linkers (UiO-66) as a core-structure and BPYDC linkers (UiO-67-BPY) as a shell-structure was developed (UiO-67-BPY@UiO-66). The combination of several techniques such as XRD, FTIR, SEM, TEM, and surface area analysis etc. were applied for the characterization and confirmed a core-shell structure of UiO-67-BPY@UiO-66. Taking advantage of the high porous stability of the core-structure (UiO-66) and the presence of active Lewis basic sites from the bipyridinic linker in the shell layer (UiO-67-BPY) could be advantageous for basic-catalyzed reactions. The synthesized core-shell material was applied as a heterogeneous catalyst for the Knoevenagel condensation as a model reaction. An excellent catalytic performance was obtained by the core-shell material over traditional MOFs and other previous reports based on MOFs. The excellent dispersion of the active sites (Lewis basic) in the outer layer of the designed core-shell structure was a breakthrough to prevent mass diffusion limitation during catalysis. Additionally, the catalyst can be recycled and maintained its high catalytic performance at least for four cycles. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • The core-structure UiO-66 combined with shell-structure UiO-67-BPY was explored. • Silver (Ag) was selected for the selective metal incorporation. • Excellent Ag-dispersion via coordination with the bipyridinic groups was obtained. • Ag-UiO-67-BPY@UiO-66 showed excellent yields and recyclability for CO2 fixation. • Carboxylation was performed using a low Ag-loading under mild reaction conditions. Abstract A core-shell metal-organic frameworks (MOF@MOF) based on the Zr-MOFs assembly from core-structure UiO-66 combined with shell-structure UiO-67-BPY were explored. The synthesized materials were characterized via XRD, FTIR, SEM, TEM, and surface area analysis, etc. indicating the presence of a core-shell structure of UiO-66@UiO-67-BPY. Furthermore, incorporation of the bipyridinic (BPY) group in the linker used to construct the shell layer (UiO-67-BPY) could coordinate with active metal species and thus create an advantage for site-selective metal incorporation in the core-shell structure. Silver (Ag) was selected for the selective metal incorporation and an excellent Ag-dispersion via coordination with the bipyridinic groups in the UiO-67-BPY layer of the core-shell material was obtained. The synthesized material (UiO-66@UiO-67-BPY-Ag) was successfully applied as a heterogeneous catalyst for the CO 2 fixation via carboxylation of terminal alkynes. The catalytic material showed excellent yields using at a low Ag-loading under mild reaction condition (50 °C, 1 bar). Moreover, the catalyst can be recycled for at least 5 times maintaining a stable catalytic performance. Interestingly, the high catalytic activity of the synthesized material demonstrated clearly the beneficial advantage of the metalated core-shell structure over the reported routes to synthesize silver catalysts such as encapsulated Ag nanoparticles (AgNP@MOF) or Ag-bidentately coordinated on traditional MOFs applying the same reaction model. [ABSTRACT FROM AUTHOR]