Intercalation of laminar Cu-Al LDHs with molecular TCPP(M) (M = Zn, Co, Ni, and Fe) towards high-performance CO2 hydrogenation catalysts.

A confined space is broadly applied to enhance the dispersion and limit the aggregation of catalytically active sites, especially at high temperatures. In this work, we provided an efficient approach to immobilize transition metal ions (e.g., Zn2+, Co2+, Ni2+, and Fe2+) into the confined space of laminar Cu-Al layered double hydroxides (LDHs) using a range of molecular metalloporphyrins (viz., TCPP(M)) as shuttles. The deprotonated TCPP(M) not only provides nitrogen-based coordination sites to anchor a series of transition metal ions, but also intercalates and diffuses facilely into the interlayer gallery of LDHs by ion exchange. The obtained TCPP(M)@Cu-Al LDHs were then used as solid precursors for the fabrication of a series of heterogeneous catalysts for CO2 hydrogenation via high-temperature calcination. Two restriction forces contributed to the enhanced dispersion of the active species over the catalyst surface structures. Remarkably, the transition metals positioned within the confined space of LDHs significantly affected the catalytic performance of CO2 hydrogenation. Mainly CO, methanol, and methane were found as the C1 products, and their selectivities are highly dependent on the reaction intermediates, as suggested by the in situ DRIFTS study. Moreover, the designed catalysts fabricated via molecular TCPP(M) intercalation exhibited much better performance than the conventional catalysts derived from surface-supported CA-LDHs, due to their better metal dispersion and smaller particle size.

3D-Printed metal-organic frameworks within biocompatible polymers as excellent adsorbents for organic dyes removal.

Three-dimensional (3D) printing technique has received exceptional global attention as it can create a myriad of high-resolution architectures from digital models. In the present study, 3D-printed metal-organic frameworks (MOFs) were shaped into several geometries via direct ink writing, which overcomes the instability and high-pressure drop of powdery MOF during the flow of gas or liquid streams. The inclusion of a blend of calcium alginate and gelatin (CA-GE) as biocompatible binder allowed for easy writing and an enhanced mechanical property. Besides, it was found that the printing geometry (square, hexagon, and circle), MOF loading amount, and MOF size also greatly influenced the adsorptive performance. For instance, the methylene blue adsorption efficiency of CA-GE scaffolds without MOF was only 43.6%, while the printed MOF/CA-GE sample exhibited 99.8% adsorption efficiency at 20 min. Both the inherent microporous structure of MOFs and meso/macroporous structures of the 3D matrix contributed to the excellent adsorption properties towards a variety of organic dyes and their mixtures. Furthermore, the 3D-printed adsorbents can be easily regenerated in dilute acid solution and reused for at least 7 times without performance loss. In contrast, the powdery MOF can only be repeatedly used for at most 2 times.