Metal–organic frameworks (MOFs) have high porosity and surface area, making them ideal candidates for adsorption-mediated applications. One high-value application is the removal of uremic toxins from solution for dialysis. Previous studies have reported adsorptive removal of the uremic toxin p-cresyl sulfate from solution via zirconium-based MOFs, but a specific analysis of parameters contributing to adsorptive uptake is needed to clarify differences in uptake performance between MOFs. We synthesized zirconium 1,3,5-benzenetricarboxylate (MOF-808) and an iron-based analog, MIL-100­(Fe), and compared their adsorptive uptake with previously reported values of other zirconium-based MOFs. MIL-100­(Fe) adsorbed three times more p-cresyl sulfate from solution on a per mass basis than MOF-808 and had a greater adsorption efficiency than 75% of previously reported Zr-based MOFs. We compared p-cresyl sulfate uptake by MOFs as a function of BET surface area, number of aromatic carbons in the organic linker, internal cage diameter, and pore window diameter. There is poor correlation between p-cresyl sulfate uptake and each of the variables considered, but the number of aromatic carbons of the MOF linker was a better predictor of uptake than BET surface area (R 2 = 0.7034 and 0.1430, respectively), and pore window aperture was a better predictor of uptake than the pore cage diameter (R 2 = 0.4780 and 0.0383, respectively). We hypothesize that the greater adsorptive capacity of MIL-100­(Fe) compared to MOF-808 results from direct coordination of p-cresyl sulfate to vacant metal sites in the MOF, and the total adsorption may be accounted for by some combination of adsorptive interactions occurring at both metal and organic linker sites near to the exterior particle surface. The adsorptive uptake of p-cresyl sulfate by MIL-100­(Fe) was observed to increase with p-cresyl sulfate content, mass of MIL-100­(Fe), and volume of p-cresyl sulfate solution; the mass of MIL-100­(Fe) had the greatest effect on total adsorption.

Metal–organic framework nanosheets (MOFNs) are promising materials for heterogeneous catalysis systems where active metal sites are positioned on particle exterior surfaces. The hypothesis that intrapore metal sites are active for catalysis has been disproven for certain systems, and therefore the synthesis of MOF particles with increased external surface area and density of metal active sites is needed. MOFNs provide an increased proportion of metal sites accessible to substrates that experience limited or no diffusion into MOF pores compared to MOF particles with other morphologies such as octahedra. However, developing synthetic methods to generate a variety of MOFNs remains an experimental challenge, particularly for water-stable materials. Herein, we use a three-layer method to synthesize the nanosheet particles of a new MOF, CuBDTri (where H2BDTri = 1,4-di­(1H-1,2,3-triazol-5-yl)­benzene). Scanning electron microscopy (SEM), powder X-ray diffraction (pXRD), Brunauer–Emmett–Teller (BET) analysis, inductively coupled plasma atomic emission spectroscopy (ICP-AES), and acid digestion with time-of-flight mass spectrometry (TOF-MS) were used to characterize the newly synthesized CuBDTri nanosheets. Both the synthetic method and linker identity were shown to impact the anisotropic growth of MOF particles with nanosheet morphologies. Importantly, this is the first report of using the three-layer method to synthesize MOFNs with Cu–N linkages, meaning that the three-layer method is (i) more broadly applicable than previously known (having only been used previously to synthesize nanosheets with Cu-oxo linkages) and (ii) can be used to synthesize water-stable Cu-MOFNs in situ (a key result, given MOFs with Cu-oxo linkages usually exhibit poor water stability). CuBDTri nanosheets are also more catalytically active on a per-total-Cu-atom basis for a standardized test reaction (nitric oxide (NO) generation from S-nitrosoglutathione (GSNO)) than previously studied octahedral particles of the MOF CuBTTri (where H3BTTri = 1,3,5-tris­(1H-1,2,3-triazol-5-yl)­benzene), supporting the hypothesis that MOFNs are superior to particles with other morphologies for reactions where catalytic activity is limited to particle exterior surfaces (such as the NO generation reaction).

The analysis of protein in algal biomass is one of the most critical areas of commercial development of algae characterization for nutritional or other high value applications. A new rapid and accurate method is required that can be widely implemented and that is free from interferences from the complex algal biomass matrix. We developed a simple spectrophotometric method for primary amino acid quantification bulk measurement in an acid hydrolyzed algal biomass preparation, as an alternative to the more labor-intensive amino HPLC acid analysis or less specific nitrogen-to-protein conversion. We have validated an O-phthalaldehyde (OPA)-based derivatization method, showing accurate and linear quantification for standard reference amino acids as well as mixtures, mimicking the amino acid complexity found in algal biomass. The presence of interferences that may be derived from the complex biomass biochemical composition was tested during the method validation phase. We document the application of a novel method of OPA derivatization with 3-mercaptopropionic acid (3MPA) to determine the total amino acid content of harvested algal biomass collected from different, controlled cultivation conditions and demonstrated a within 10% accuracy against a reference measurement of amino acid content in at least 4 species and 10 algal biomass samples, across early, mid, and late-stages of cultivation.

Cannabinoids are important industrial analytes commonly assayed with high-pressure liquid chromatography (HPLC). In this study, we evaluate the suitability of MIL-53(Al), a commercially available metal−organic framework (MOF), as a stationary phase for cannabinoid separations. The suitability of an MOF for a given separation is hypothesized to be limited by the ability of a given molecule to enter the pore of the MOF. To evaluate the extent of possible adsorptive interactions between cannabinoids and the interior surface area of MIL-53(Al), the radii of gyration (R g ) and solvent-accessible surface areas were calculated for three cannabinoids, namely, cannabidiol, cannabinol, and Δ9-tetrahydrocannabinol, as well as the MOF. These values were used to calculate the theoretical adsorption capacity of the MOF, using four competing adsorption models. The R g of cannabinoids (4.1 Å) is larger than one MOF pore aperture dimension (4.0 × 5.0 Å). The adsorption capacity was measured by relating a decrease in the cannabinoid concentration in acetonitrile when exposed to 100 mg of MOF. The cannabinoid uptake by the MOF was estimated using the relative standard deviation (RSD) of the soaking solution assay, as the decomposition-corrected RSD as uptake (DCRU). The DCRU was calculated as 0.007 ± 0.004 μg cannabinoids /mg MOF . These findings indicate that most of the MOF surface area was inaccessible for adsorption by cannabinoids due to size-exclusion effects. The implication of this work is that the suitability of an MOF for adsorptive separations, such as liquid chromatography, must have an upper limit for the size of the analyte. Additionally, MOFs may generally be more suitable for separations in the gas phase, where adsorbates are not hindered by the presence of a solvation shell.

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