Porous Materials -Metal-Organic Frameworks 2012 Nanocamp NCMN, UNL Dr. Jian Zhang & Jacob Johnson Department of Chemistry
Porous Materials -Metal-Organic Frameworks
2012 Nanocamp NCMN, UNL
Dr. Jian Zhang & Jacob Johnson
Department of Chemistry
What does a chemist do?
• Chemists observe and study
• Chemists study the composition, assembly, properties, and reactivity of matter (atoms, molecules, materials)
• Chemistry is considered as the central science
Chemistry is the Central Science
Chemistry
Medicine
Environmental Sciences
Astronomy
Biology
Geology
Physics Materials Science
Pharmaceutical
What does a chemist do?
• Chemists make compounds and materials
– Synthetic chemistry
• Measure properties of materials
– Analytical chemistry
• Model chemical reactions and materials structures
– Theoretical and computational
chemistry
Penicillin
What does it take to become a chemist?
• Strong interest in science • Strong academic performance • 4+ years of college • Graduate degree (2-4 years)
– Hundreds of graduate schools in the US
• Diverse and rewarding career – Creativity is important – Worldwide industry – Work on important global problems
• Energy • Pollution • Disease
The Zhang’s Group Research
Metal-organic Frameworks Covalent-organic Frameworks Porous polymer networks
Porous Materials in Nature
Sandstones
Sea Sponge
Butterfly Wings
Egg Shells Snow
Coral Soil Bone Lungs
Lemons
Artificial Porous Materials
Insulation
Cake
Concrete
Bread Ceramics
Chalk Brick Paper
Sponges
Clothing
Pore Type (size)
Micropores (< 2 nm) Mesopores (2-50 nm) Macropores (< 50 nm)
Surface of a chicken egg shell Carbon membrane Monolithic column
Microporous Materials
• A microporous material is a material containing pores with diameters less than 2 nm
• Activated Carbons
• Zeolites
• Metal-organic frameworks
• Covalent organic frameworks
• Microporous polymer
Applications
– Microporous materials • Activated carbons
– The small size of their pores gives them great surface area… they can adsorb a large amount of gas directly on to their surface. Popular support for some catalyst metals (especially palladium and platinum). ρ~ 2g/cm3
• Zeolites – The narrow size distribution of their pores makes them very useful
for gas separation. Also used as catalysts because of acid sites in the pores. ρ~ 4g/cm3
• Metal organic frameworks – Their huge surface area and pore volume makes them potentially
useful for gas sequestration/storage. ρ< 0.5g/cm3
Activated Carbons
Rice Husk Nut Shells
Coconut Fiber Biomass
Made from a variety of materials:
Organic, non-ordered structure
Zeolites – Micropores are part of their crystal structure:
• Most are synthetic
• Alumino-silicates
• Silicalite = no aluminum
• Cation can be H+, Na+, Ca2+, NH4+, etc
• Pore shape needs to be incorporated into pore size calculation for accurate results
• Some adsorbates are better than others
Inorganic, ordered structure
Metal Organic Frameworks MOFs
– Synthetic materials
– Also called coordination polymers
– Similar materials without metals are called COFs… covalent coordination polymers
– Still a very active research area
Inorganic-Organic Hybrid, ordered structure
Metal Organic Frameworks MOFs
Zn4O tetrahedra (blue) are joined by organic linkers (O, red, C, black), giving an extended 3D cubic framework with inter-connected pores of 11.2 Å aperture width and 18.5Å pore (yellow sphere) diameter
Metal Organic Frameworks MOFs
Breathable MOFs
• Petroleum dependence → U.S. imports 55% of its oil expected to grow to 68% in 2025 • Hydrogen as energy carrier → clean, efficient, and can be derived from domestic resources
Renewable (biomass, hydro, wind, solar, and geothermal)
Fossil fuels (coal ,natural gas, etc.)
Nuclear Energy
Hydrogen storage
Hydrogen Storage in Nano-Porous Materials
• Hydrogen storage is a critical enabling technology for the acceptance of hydrogen powered vehicles • Storing sufficient hydrogen on board to meet consumers requirements (eg. driving range, cost, safety, and performance) is a crucial technical parameter • No approach currently exists that meets technical requirement. (driving range > 300 miles)
• U.S. DoE → develop on board storage systems achieving 6 and 9 wt% for 2010 and 2015
Hydrogen storage
Hydrogen Storage in Nano-Porous Materials
Current Challenges with H2 Storage Options
Compressed Hydrogen -High pressure (500-700 atm), -Expensive storage container Liquid Hydrogen -Expensive cooling system required -High energy cost to liquefy H2
Complex and Metal Hydrides -Poor reversibility -Require high temperature and pressure (>100 ˚C and >100 atm)
MOFs as hydrogen storage materials
~ 3% wt @ 77 K, 1 atm
CO2 Sequestration
MOFs as CO2 storage materials
38.5 wt% @ 273 K, 1 atm
MOF Construction
Organic Linkers Metal Nodes
Mn2+
109.5° 90° 90°
120°
Tetrahedral Octahedral Trigonal Bipyrimidal