The use of a metal–organic framework (MOF) as a support for the in situ immobilization of enzymes was explored. The MOF support, a Basolite F300‐like material, was prepared from FeCl3 and the tridentate linker trimesic acid. Immobilization of alcohol dehydrogenase, lipase, and glucose oxidase was performed in situ under mild conditions (aqueous solution, neutral pH, and at room temperature) in a rapid and facile manner with retention of activity for at least 1 week. The catalytic activities of lipase and glucose oxidase were similar to the activities of the free enzymes; with alcohol dehydrogenase, there was a substantial decrease in activity on immobilization that may arise from diffusion limitations. The approach demonstrates that a MOF material, prepared from cheap and commercially available materials, can be successively utilized to prepare stable and catalytically active biocatalysts in a rapid and facile manner.

Graphical abstractResearch Highlights: Semi-crystalline Fe-BTC MOF material is an efficient support for enzymes  It can be used by either in-situ or post-synthesis approaches  The in-situ (one-step) biocatalysts are more active and have lower enzyme leaching  This enzyme support improves the benefits given by some other MOF-based supports ABSTRACT. Metal-organic frameworks (MOFs) have revolutionized the potential applications of nanoporous materials. One of the most recent and promising applications of these materials is their use as supports for enzyme immobilization. In this context, the in-situ (one-step) methodologies, which do not require the use of MOFs with pores larger than the enzyme to be immobilized, seem to be particularly encouraging. This work presents a systematic study of the semi-crystalline Fe-BTC MOF material (commercialized as Basolite F300) employed as support of the enzymes laccase and lipase through either in-situ or postsynthesis methodology. The presence of the enzyme in the resultant solid biocatalysts was proved by CHNS chemical analysis, thermogravimetric analysis, Bradford assays and by SDS-PAGE electrophoresis. The enzymatic activity of the resultant Fe-BTC-based biocatalysts was also tested. The in-situ approach is particularly relevant due to various reasons: (i) the enzyme immobilization is given in one step; (ii) it is rapid (10 minutes); (iii) it is very efficient in terms of encapsulation capacity (≥ 98 % for laccase and ≥ 87 % for lipase); (iv) the enzymes are fully retained and no leaching is observed after an initial release of only around 10% of the enzyme molecules weakly immobilized; and (v) the activity of the retained enzyme can be substantially maintained (97 % with respect to the free enzyme in the case of lipase). Any of these parameters systematically improves these given by the post-synthesis (two-step) approach. Moreover, Fe-BTC widely surpasses the benefits given by other MOF-based supports either by in-situ or postsynthesis approaches.

Metal-organic framework (MOF) materials possess the widest versatility in structure, composition, and synthesis procedures amongst the known families of materials. On the other hand, the extraordinary affinity between MOFs and enzymes has led to widely investigating these materials as platforms to support these catalytic proteins in recent years. In this work, the MOF material NH2-MIL-53(Al) has been tested as a support to immobilize by one-step methodology (in situ) the enzyme lipase CaLB from Candida antarctica by employing conditions that are compatible with its enzymatic activity (room temperature, aqueous solution, and moderate pH values). Once the nature of the linker deprotonating agent or the synthesis time were optimized, the MOF material resulted in quite efficient entrapping of the lipase CaLB through this in situ approach (>85% of the present enzyme in the synthesis media) while the supported enzyme retained acceptable activity (29% compared to the free enzyme) and had scarce enzyme leaching. The equivalent post-synthetic method led to biocatalysts with lower enzyme loading values. These results make clear that the formation of MOF support in the presence of the enzyme to be immobilized substantially improves the efficiency of the biocatalysts support for retaining the enzyme and limits their leaching.

In this work, we report the mechanical properties of an alternative material based on a mixture of natural clay and ferruginous sand in pellet form for CO2 capture. These raw materials were collected from Ecuador, and they contain iron and titanium oxides from volcanic origin. To evaluate the effect of the sand content on the mechanical properties of pellets, the samples were manually prepared with 0 (control sample), 15, and 25 wt.% sand contents and analyzed using free-fall drop impact and uniaxial compression tests. The uniaxial compression test was carried out under three conditions: using sieved sand, using sand without sieving, and under wet conditions. The sand contents caused the drop number to decrease in the free-fall drop impact test. From the uniaxial compression test, the compressive strength, elastic modulus, and toughness were calculated. The elastic modulus showed a better performance for samples with lower porosity. The compressive strength demonstrated higher values for samples with 15 wt.% sand contents than for samples with the other sand contents. The toughness values did not significantly change. It was evidenced that the porosity, mineral composition, and humidity exerted an influence during the mechanical tests. The mineral phases were analyzed by X-ray diffraction, and quantitative analysis based on whole-powder-pattern fitting revealed that the iron and titanium oxide contents increased as the concentration of sand in the pellets increased.