The desulfurization property of conventional mixed matrix membranes (MMMs) cannot meet the necessary demand due to particles aggregation and interface defects. Here, we put forward a layer-by-layer (LBL) approach to make a novel PEG@ZIF-8/poly­(vinylidene difluoride)­(PVDF) composite membrane for pervaporation desulfurization. In this way, a ZIF-8 layer is covered on the surface of the PVDF porous membrane via an in situ growth method. Then, a PEG layer is covered on the ZIF-8 layer by a casting method. Compared with pristine PEG membranes, the separation performance of the ZIF-8@PEG/PVDF nanocomposite membrane increased significantly. This can be attributed to the homogeneous ZIF-8 particle layer and better compatibility between the poly­(ethylene glycol) (PEG) matrix and ZIF-8 particles. The membrane achieves a maximum total flux of 3.08 kg·m–2·h–1 at the third in situ growth cycles of ZIF-8 particles and a maximum sulfur enrichment factor of 7.6 at the sixth in situ growth cycles of ZIF-8 particles.

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In this work, two new metal-metalloporphyrin frameworks (MMPFs), namely, MMPF-12 and MMPF-13, having unique structural formulas as [Mn24O78­(Mn-dcdbp)12] and [Mn8.65(dcdbp)8]­(DMF)14(H2O)8, respectively, were synthesized via the reaction of the custom-designed porphyrin ligand 5,15-bis­(3,5-dicarboxyphenyl)-10,20-bis­(2,6-dibromophenyl) porphyrin (dcdbp) and hydrated manganese nitrate under solvothermal conditions. Single-crystal X-ray diffraction analysis reveals three-dimensional porous structures with MMPF-12 exhibiting nearly complete metalation of the ligand, whereas MMPF-13, unusually, contains only a small fraction of metalated porphyrin. Gas sorption studies attest to a permanent porosity together with selective adsorption of CO2 over CH4. Additionally, both MMPFs catalyzed CO2 cycloaddition of electronically and sterically substituted epoxide substrates, thereby providing access to important products under mild conditions. Results also showed that the ligand-metalated MMPF-12, containing trimer Mn clusters, has a higher catalytic activity than its congener MMPF-13, which has only dimer clusters. Thus, Mn clusters likely play an important role in both the structure of the MMPFs and their activity toward the transformation of CO2, with the enhanced catalytic activity being ascribed to the conserved porous structure.

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