Activity Trends in the Propane Dehydrogenation Reaction Catalyzed by MIII Sites on an Amorphous SiO2 Model: A Theoretical Perspective

One class of particularly active catalysts for the Propane Dehydrogenation (PDH) reaction are well-defined M(III) sites on amorphous SiO2. In the present work, we focus on evaluating the catalytic trends of the PDH for four M(III) single-sites (Cr, Mo, Ga and In) on a realistic amorphous model of SiO2 using density functional theory-based calculations and the energetic span model. We considered a catalytic pathway spanned by three reaction steps taking place on selected MIII–O pair of the SiO2 model: σ-bond metathesis of propane on a MIII–O bond to form M-propyl and O–H group, a β-H transfer step forming M–H and propene, and the H–H coupling step producing H2 and regenerating the initial M–O bond. With the application of the energetic span model, we found that the calculated catalytic activity for Ga and Cr is comparable to the ones reported at the experimental level, enabling us to benchmark the model and the methodology used. Furthermore, results suggest that both In(III) and Mo(III) on SiO2 are potential active catalysts for PDH, provided they can be synthesized and are stable under PDH reaction conditions.

Advances in heterometallic ring-opening (co)polymerisation catalysis

Truly sustainable plastics require renewable feedstocks coupled with efficient production and end-of-life degradation/recycling processes. Some of the most useful degradable materials are aliphatic polyesters, polycarbonates and polyamides, which are often prepared via ring-opening (co)polymerisation (RO(CO)P) using an organometallic catalyst. While there has been extensive research into ligand development, heterometallic cooperativity offers an equally promising yet underexplored strategy to improve catalyst performance, as heterometallic catalysts often exhibit significant activity and selectivity enhancements compared to their homometallic counterparts. This review describes advances in heterometallic RO(CO)P catalyst design, highlighting the overarching structure-activity trends and reactivity patterns to inform future catalyst design.

Increasing the CO2 Reduction Activity of Cobalt Phthalocyanine by Modulating the σ-donor Strength of Axially Coordinating Ligands

<p>Axial coordination of a pyridyl moieties to CoPc (either exogenous or within poly-4-vinylpyridine polymer) dramatically increases the complex’s activity for CO₂RR. It has been hypothesized that axial coordination to the Co active site leads to an increase in the Co dz² orbital energy, which increases the complex’s nucleophilicity and facilitates CO₂ coordination compared to the parent CoPc complex. The magnitude of the energy increase in the Co dz² orbital should depend on the σ-donor strength of the axial ligand—a stronger σ-donating ligand (L) will increase the overall CO₂RR activity of axially coordinated CoPc(L) and vice versa. To test this, we have studied a series of CoPc(L) complexes where the σ-donor strength of L is varied. We show that CoPc(L) reduces CO₂ with an increased activity as the σ-donor ability of L is increased. These observed electrochemical activity trends are correlated with computationally-derived CO₂ binding energy and charge transfer terms as a function of σ-donor strength. The findings of this study supports our hypothesis that the increased CO₂RR activity observed upon axial coordination to CoPc is due to the increased energy of the dz² orbital, and highlight an important design consideration for macrocyclic MN₄-based electrocatalysts.</p><p> </p><p> </p>

Increasing the CO2 Reduction Activity of Cobalt Phthalocyanine by Modulating the σ-donor Strength of Axially Coordinating Ligands

<p>Axial coordination of a pyridyl moieties to CoPc (either exogenous or within poly-4-vinylpyridine polymer) dramatically increases the complex’s activity for CO₂RR. It has been hypothesized that axial coordination to the Co active site leads to an increase in the Co dz² orbital energy, which increases the complex’s nucleophilicity and facilitates CO₂ coordination compared to the parent CoPc complex. The magnitude of the energy increase in the Co dz² orbital should depend on the σ-donor strength of the axial ligand—a stronger σ-donating ligand (L) will increase the overall CO₂RR activity of axially coordinated CoPc(L) and vice versa. To test this, we have studied a series of CoPc(L) complexes where the σ-donor strength of L is varied. We show that CoPc(L) reduces CO₂ with an increased activity as the σ-donor ability of L is increased. These observed electrochemical activity trends are correlated with computationally-derived CO₂ binding energy and charge transfer terms as a function of σ-donor strength. The findings of this study supports our hypothesis that the increased CO₂RR activity observed upon axial coordination to CoPc is due to the increased energy of the dz² orbital, and highlight an important design consideration for macrocyclic MN₄-based electrocatalysts.</p><p> </p><p> </p>

Increasing the CO2 Reduction Activity of Cobalt Phthalocyanine by Modulating the σ-donor Strength of Axially Coordinating Ligands

<p>Axial coordination of a pyridyl moieties to CoPc (either exogenous or within poly-4-vinylpyridine polymer) dramatically increases the complex’s activity for CO₂RR. It has been hypothesized that axial coordination to the Co active site leads to an increase in the Co dz² orbital energy, which increases the complex’s nucleophilicity and facilitates CO₂ coordination compared to the parent CoPc complex. The magnitude of the energy increase in the Co dz² orbital should depend on the σ-donor strength of the axial ligand—a stronger σ-donating ligand (L) will increase the overall CO₂RR activity of axially coordinated CoPc(L) and vice versa. To test this, we have studied a series of CoPc(L) complexes where the σ-donor strength of L is varied. We show that CoPc(L) reduces CO₂ with an increased activity as the σ-donor ability of L is increased. These observed electrochemical activity trends are correlated with computationally-derived CO₂ binding energy and charge transfer terms as a function of σ-donor strength. The findings of this study supports our hypothesis that the increased CO₂RR activity observed upon axial coordination to CoPc is due to the increased energy of the dz² orbital, and highlight an important design consideration for macrocyclic MN₄-based electrocatalysts.</p><p> </p><p> </p>