Spatial segregation of catalytic sites within Pd doped H-ZSM-5 for fatty acid hydrodeoxygenation to alkanes.

Spatial control over features within multifunctional catalysts can unlock efficient one-pot cascade reactions, which are themselves a pathway to aviation biofuels via hydrodeoxygenation. A synthesis strategy that encompasses spatial orthogonality, i.e., one in which different catalytic species are deposited exclusively within discrete locations of a support architecture, is one solution that permits control over potential interactions between different sites and the cascade process. Here, we report a Pd doped hierarchical zeolite, in which Pd nanoparticles are selectively deposited within the mesopores, while acidity is retained solely within the micropores of ZSM-5. This spatial segregation facilitates hydrodeoxygenation while suppressing undesirable decarboxylation and decarbonation, yielding significant enhancements in activity (30.6 vs 3.6 moldodecane molPd-1 h-1) and selectivity (C12:C11 5.2 vs 1.9) relative to a conventionally prepared counterpart (via wet impregnation). Herein, multifunctional material design can realise efficient fatty acid hydrodeoxygenation, thus advancing the field and inspiring future developments in rationalised catalyst design.

Polyvalent Glycan Functionalized Quantum Nanorods as Mechanistic Probes for Shape-Selective Multivalent Lectin-Glycan Recognition.

Multivalent lectin-glycan interactions (MLGIs) are widespread in biology and hold the key to many therapeutic applications. However, the underlying structural and biophysical mechanisms for many MLGIs remain poorly understood, limiting our ability to design glycoconjugates to potently target specific MLGIs for therapeutic intervention. Glycosylated nanoparticles have emerged as a powerful biophysical probe for MLGIs, although how nanoparticle shape affects the MLGI molecular mechanisms remains largely unexplored. Herein, we have prepared fluorescent quantum nanorods (QRs), densely coated with α-1,2-manno-biose ligands (QR-DiMan), as multifunctional probes to investigate how scaffold geometry affects the MLGIs of a pair of closely related, tetrameric viral receptors, DC-SIGN and DC-SIGNR. We have previously shown that a DiMan-capped spherical quantum dot (QD-DiMan) gives weak cross-linking interactions with DC-SIGNR but strong simultaneous binding with DC-SIGN. Against the elongated QR-DiMan, DC-SIGN retains similarly strong simultaneous binding of all four binding sites with a single QR-DiMan (apparent K d ≈ 0.5 nM, ∼1.8 million-fold stronger than the corresponding monovalent binding), while DC-SIGNR gives both weak cross-linking and strong individual binding interactions, resulting in a larger binding affinity enhancement than that with QD-DiMan. S/TEM analysis of QR-DiMan-lectin assemblies reveals that DC-SIGNR's different binding modes arise from the different nanosurface curvatures of the QR scaffold. The glycan display at the spherical ends presents too high a steric barrier for DC-SIGNR to bind with all four binding sites; thus, it cross-links between two QR-DiMan to maximize binding multivalency, whereas the more planar character of the cylindrical center allows the glycans to bridge all binding sites in DC-SIGNR. This work thus establishes glycosylated QRs as a powerful biophysical probe for MLGIs not only to provide quantitative binding affinities and binding modes but also to demonstrate the specificity of multivalent lectins in discriminating different glycan displays in solution, dictated by the scaffold curvature.