Search research articles

ABOUT JoVE

Overview Leadership Blog JoVE Help Center

AUTHORS

Publishing Process Editorial Board Scope & Policies Peer Review FAQ Submit

LIBRARIANS

Testimonials Subscriptions Access Resources Library Advisory Board FAQ

RESEARCH

JoVE Journal Methods Collections JoVE Encyclopedia of Experiments Archive

EDUCATION

JoVE Core JoVE Business JoVE Science Education JoVE Lab Manual Faculty Resource Center Faculty Site

Terms & Conditions of Use

Related Concept Videos

Turnover Number and Catalytic Efficiency

Turnover Number and Catalytic Efficiency

The turnover number of an enzyme is the maximum number of substrate molecules it can transform per unit time. Turnover numbers for most enzymes range from 1 to 1000 molecules per second. Catalase has the known highest turnover number, capable of converting up to 2.8×106 molecules of hydrogen peroxide into water and oxygen per second. Lysozyme has the lowest known turnover number of half a molecule per second.
Chymotrypsin is a pancreatic enzyme that breaks down proteins during digestion....

Catalytically Perfect Enzymes

Catalytically Perfect Enzymes

The theory of catalytically perfect enzymes was first proposed by W.J. Albery and J. R. Knowles in 1976. These enzymes catalyze biochemical reactions at high-speed. Their catalytic efficiency values range from 108-109 M-1s-1. These enzymes are also called 'diffusion-controlled' as the only rate-limiting step in the catalysis is that of the substrate diffusion into the active site. Examples include triose phosphate isomerase, fumarase, and superoxide dismutase.

Most enzymes...

Catalysis

Catalysis

The presence of a catalyst affects the rate of a chemical reaction. A catalyst is a substance that can increase the reaction rate without being consumed during the process. A basic comprehension of a catalysts’ role during chemical reactions can be understood from the concept of reaction mechanisms and energy diagrams.

Reduction of Alkenes: Catalytic Hydrogenation

Reduction of Alkenes: Catalytic Hydrogenation

Alkenes undergo reduction by the addition of molecular hydrogen to give alkanes. Because the process generally occurs in the presence of a transition-metal catalyst, the reaction is called catalytic hydrogenation.
Metals like palladium, platinum, and nickel are commonly used in their solid forms — fine powder on an inert surface. As these catalysts remain insoluble in the reaction mixture, they are referred to as heterogeneous catalysts.
The hydrogenation process takes place on the...

Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation

Reduction of Alkynes to cis-Alkenes: Catalytic Hydrogenation

Introduction
Like alkenes, alkynes can be reduced to alkanes in the presence of transition metal catalysts such as Pt, Pd, or Ni. The reaction involves two sequential syn additions of hydrogen via a cis-alkene intermediate.

You might also read

Related Articles

Articles linked to this work by shared authors, journal, and citation graph.

Sort by

Same author

Guiding the De Novo Synthesis of Open Metal Frameworks Through Low-Symmetry Bent Linker for Hydrogen Isotope Separation.

Small (Weinheim an der Bergstrasse, Germany)·2026

Same author

Interfacial Growth of 420 nm Ultrathin and Dense MOFs for Composite Electrolyte to Reduce Li<sup>+</sup> Conduction Resistance and Inhibit Lithium Dendrite.

Advanced science (Weinheim, Baden-Wurttemberg, Germany)·2026

Same author

Windowed Symmetry Pulses for Enhanced Heteronuclear Dipolar Recoupling in Solid-State MAS NMR.

Precision chemistry·2026

Same author

Wearable Self-Powered Biomedical Smart Sensors Deriving from E-Waste.

Nano letters·2026

Same author

Sulfur-Functionalized Hyper-Cross-Linked Carbon Molecular Sieve Membranes with Enhanced Ethylene/Ethane Separation Performance.

Langmuir : the ACS journal of surfaces and colloids·2026

Same author

High-Selectivity Proton Exchange Membranes with Low Ion Exchange Capacity and Hydrophobic Side Chain-Induced Micro-Phase Separation for Vanadium Redox Flow Batteries.

Membranes·2026

Search research articles

Related Experiment Video

Updated: Sep 9, 2025

Optimization of the Ugi Reaction Using Parallel Synthesis and Automated Liquid Handling

Optimization of the Ugi Reaction Using Parallel Synthesis and Automated Liquid Handling

Published on: November 11, 2008

Beyond Density: Unveiling the Trade-Off in Catalytic Site Optimization Using Defect-Engineered UiO-66.

Guo-Ying Han¹, Yi Ji², Xiang-Yu Li³

¹School of Chemistry, Dalian University of Technology, Dalian, 116024, China.

Advanced Science (Weinheim, Baden-Wurttemberg, Germany)

|September 2, 2025

Summary

Increasing catalytic sites in metal-organic frameworks (MOFs) doesn't always boost performance. Too many sites can cause self-adsorption, hindering reactions and lowering catalytic activity.

Keywords:

MOFs catalytic sites density cluster defects defect types linker defects

More Related Videos

Tuning Oxide Properties by Oxygen Vacancy Control During Growth and Annealing

Tuning Oxide Properties by Oxygen Vacancy Control During Growth and Annealing

Published on: June 9, 2023

Fabrication and Testing of Catalytic Aerogels Prepared Via Rapid Supercritical Extraction

Fabrication and Testing of Catalytic Aerogels Prepared Via Rapid Supercritical Extraction

Published on: August 31, 2018

Related Experiment Videos

Last Updated: Sep 9, 2025

Optimization of the Ugi Reaction Using Parallel Synthesis and Automated Liquid Handling

Optimization of the Ugi Reaction Using Parallel Synthesis and Automated Liquid Handling

Published on: November 11, 2008

Tuning Oxide Properties by Oxygen Vacancy Control During Growth and Annealing

Tuning Oxide Properties by Oxygen Vacancy Control During Growth and Annealing

Published on: June 9, 2023

Fabrication and Testing of Catalytic Aerogels Prepared Via Rapid Supercritical Extraction

Fabrication and Testing of Catalytic Aerogels Prepared Via Rapid Supercritical Extraction

Published on: August 31, 2018

Area of Science:

Materials Science
Catalysis
Chemical Engineering

Background:

Enhancing catalytic performance is crucial for chemical processes.
Strategies include boosting intrinsic activity and increasing catalytic site density.
The interplay between these strategies, particularly in metal-organic frameworks (MOFs), is not well understood.

Purpose of the Study:

To investigate the relationship between catalytic site density and catalytic performance in UiO-66 MOFs.
To compare linker-defective (UiO-66L) and cluster-defective (UiO-66C) UiO-66 MOFs with varying site densities.
To elucidate the underlying mechanisms affecting catalytic activity and diffusion.

Main Methods:

Synthesis of UiO-66L and UiO-66C MOFs with distinct catalytic site densities.
Systematic comparison of catalytic activity across four model reactions.
Diffusion-ordered spectroscopy (DOSY) and molecular dynamics (MD) simulations to study diffusion rates.
Analysis of reactant self-adsorption effects.

Main Results:

UiO-66L, despite higher Zr catalytic site density, showed lower activity than UiO-66C and defect-free UiO-66.
UiO-66C exhibited similar diffusion rates to defect-free UiO-66.
UiO-66L displayed significantly slower diffusion rates.
High catalytic site density in UiO-66L led to reactant self-adsorption and local diffusion resistance.

Conclusions:

A performance trade-off exists between catalytic site density and intrinsic activity in MOFs.
Exceeding a critical threshold of catalytic site density can negatively impact catalysis.
Defect engineering in MOFs requires careful consideration of site density effects on diffusion and overall performance.