If you’ve ever ordered a carbon molecular sieve (CMS) from our warehouse or browsed our product catalog, you might have caught a side reference to electrical conductivity in our spec sheets and thought, “Wait, this porous carbon material I know for air separation and gas purification actually conducts electricity?” It’s a question we get all the time—from process engineers at mid-sized manufacturing plants to lab managers testing new catalyst supports—and it’s one that doesn’t get enough airtime outside specialized chemistry circles. Let’s break down what CMS conductivity actually means, how it’s different from other carbon materials, why it matters for your application, and why choosing a reliable CMS supplier makes all the difference when balancing this property with the more well-known benefits of molecular sieving. Carbon Molecular Sieve
First, let’s level-set what carbon molecular sieve is for anyone new to the material. Unlike activated carbon, which has a wide, disordered pore structure that adsorbs molecules across a broad size range, CMS is manufactured with precisely controlled, uniform pores (usually between 0.3 and 1 nanometer) that act like a sieve: smaller molecules slip through and get trapped inside the pores, while larger ones pass right by. That’s why CMS is the gold standard for pressure swing adsorption (PSA) systems that produce oxygen from air, or for separating carbon dioxide from natural gas. For decades, the core selling point of CMS has been that pore size uniformity—so much so that electrical conductivity was an afterthought for most customers, a “nice to have” that only came up when a system was acting up, or when a customer needed a material that could double as an electrode in a gas sensor.
But here’s the thing about CMS: its electrical conductivity isn’t a single static number. It depends on a dozen different factors, all of which we tweak at our facility when we tailor CMS for specific use cases. Let’s start with the basics of how carbon conducts electricity. Carbon’s atomic structure, with four valence electrons that form covalent bonds with adjacent carbon atoms, leaves one free electron per atom in its sp2 hybridized lattice. That’s why pure graphite—with its tightly packed, layered sp2 structure—is an excellent electrical conductor. CMS, by contrast, is made by pyrolyzing (heating) carbon-rich precursors like coconut shells, coal, or polymer resins at very high temperatures (up to 1,000°C or more) in an oxygen-free atmosphere, then often activating it to carve out those tiny pores. The pyrolysis process breaks down the precursor’s complex molecular structure into that sp2 carbon lattice, but the pore formation process introduces defects, disorganized carbon regions, and sometimes residual impurities—all of which mess with conductivity.
So what’s the actual range of electrical conductivity for commercial CMS? Unlike graphite, which can hit 10,000 S/cm (siemens per centimeter, the standard unit for electrical conductivity) or more, most off-the-shelf CMS clocks in somewhere between 0.01 and 10 S/cm. That’s still way more conductive than activated carbon, which typically lands at 0.001 to 0.1 S/cm, but way less than graphite or even carbon nanotubes. Wait, you might be thinking—10 S/cm is a tiny number. Why does that matter? Because for many of the applications that rely on CMS, conductivity isn’t about powering a circuit; it’s about improving system efficiency, extending material lifespan, and opening up new use cases that pair gas separation with electrochemical processes. For example, if you’re using CMS in a PSA oxygen generator, if your CMS has low conductivity, it’s harder to monitor the material’s condition in real time. PSA systems rely on changes in electrical resistance across the CMS bed to track fouling, pore clogging, or material degradation—if the CMS isn’t conductive enough, those changes are impossible to detect accurately, leading to unplanned downtime or lower oxygen purity.
That’s where our expertise as a CMS supplier comes in, because we don’t just sell off-the-shelf CMS. For years, we’ve worked with customers to adjust pyrolysis temperatures, precursor selection, and post-processing steps to tune conductivity for their exact needs. Let’s say you’re a manufacturer of electrochemical gas sensors that use CMS to filter out interference gases—you need a CMS that’s porous enough to sieve out the large interfering molecules, but conductive enough to transfer the signal from the sensor electrode to the processing unit. We recently partnered with a medical device startup that was struggling with this exact problem: their initial CMS had a conductivity of 0.2 S/cm, which was too low to get a clear signal, and when they tried a higher-conductivity CMS, the larger pore size meant it couldn’t sieve out the interference gases. We adjusted their precursor from low-grade coal to high-density coconut shell, increased pyrolysis temperature by 150°C to grow a more ordered sp2 lattice, and did a mild activation step to keep pore size consistent. The result was a CMS with a conductivity of 1.8 S/cm, while maintaining the 0.36 nm pore size they needed to block interference gases. That’s the kind of balance we focus on, because conductivity isn’t a standalone spec—it’s tied directly to the core performance of the material.
Of course, there are factors that can alter CMS conductivity over time, even after it leaves our facility. Moisture is one of the biggest culprits. Water molecules are polar, and when they get absorbed into CMS pores, they can introduce ionic conductivity (conductivity from moving ions) that throws off electrical measurements, or even interfere with the sp2 carbon lattice, reducing electron flow. We’ve seen customers run their CMS beds in humid environments and see conductivity drop by 30-50% within six months, because moisture fills the tiny pores and disrupts the carbon’s conductive network. That’s why we include moisture-stabilized CMS as a standard option for outdoor PSA systems or gas separators operating in high-humidity climates—we treat the surface of the CMS with a thin hydrophobic coating that repels water, preserving both pore size and conductivity for years.
Impurities are another variable to watch. CMS made from low-quality precursors, or pyrolyzed at too low a temperature, often has residual nitrogen, sulfur, or oxygen groups attached to the carbon lattice. These groups create “charge traps” that block free electrons, lowering conductivity. For example, a CMS pyrolyzed at 600°C will have lots of oxygen-containing surface groups, leading to a conductivity as low as 0.001 S/cm, while a CMS pyrolyzed at 1,100°C will have almost no surface groups, leading to a conductivity of 5 S/cm or higher. That’s why we test every batch of our CMS for surface impurity content before it leaves our facility—we don’t cut corners on pyrolysis time or temperature, because we know that even a small impurity can make a big difference in conductivity.
Wait, let’s address a common misconception here: some people assume that higher conductivity always means better CMS. That’s not true, and it’s a mistake we see a lot of first-time buyers make. If you crank pyrolysis temperature too high, the carbon lattice becomes more ordered and conductive, but the pores start to collapse or merge—ruining the molecular sieving ability that CMS is actually valued for. For a customer using CMS for carbon dioxide separation from natural gas, a pore size of 0.3 nm is non-negotiable—any larger, and methane will slip through with the CO2, lowering separation efficiency. So we never push for the highest possible conductivity; we work to find the sweet spot where conductivity is high enough for the customer’s monitoring or electrochemical needs, but pore size remains uniform and precise.
Another area where CMS conductivity is gaining traction is in energy storage. More and more, CMS is being used as an electrode material for supercapacitors, because its tiny pores can store charge by adsorbing electrolyte ions. For these applications, conductivity is critical—you need the charge to move quickly through the electrode, which means a conductive CMS with well-connected pores. We recently collaborated with a renewable energy lab that was testing CMS electrodes for grid-scale supercapacitors; they needed a material that could handle high charge-discharge rates, so we formulated a CMS with a conductivity of 7 S/cm, a well-connected pore network, and a high surface area that maximized charge storage. The result was a supercapacitor that charged 2x faster than standard activated carbon electrodes, while maintaining 95% of its capacity after 10,000 charge cycles. That’s the kind of innovative use case that makes tuning CMS conductivity so exciting.
As a CMS supplier, we also work to educate our customers on how to measure conductivity correctly, because a lot of standard measurement methods for carbon materials don’t work for CMS. Traditional conductivity tests use bulk carbon samples, but CMS is porous, so a bulk test will give a lower reading than the actual conductive network inside the pores. We recommend using a four-point probe test on pressed CMS pellets, which accounts for the porous structure and gives a much more accurate reading. We include a free conductivity test with every custom order, because we know that spec sheets can be misleading if you don’t know how the numbers were calculated.
Let’s circle back to why this matters for you, whether you’re a plant engineer looking to upgrade your PSA system, a sensor designer developing a new medical device, or a lab researcher exploring new energy storage tech. The next time you’re comparing CMS suppliers, don’t just ask about pore size and surface area—ask about electrical conductivity. Ask how they tune that property, what factors affect it over time, and what testing methods they use to measure it. At our facility, we’ve been refining CMS for over 15 years, and we’ve found that the customers who get the best results aren’t just looking for the cheapest price or the most impressive pore size specs—they’re looking for a supplier who understands that every property of CMS is interconnected, and that conductivity plays a key role in long-term performance.
If you’re currently dealing with CMS-related issues: maybe your PSA system is giving inconsistent oxygen purity, your gas sensor is picking up interference, or your energy storage electrodes aren’t performing as expected, we can help. We’ve solved these exact problems for dozens of customers, and we can tailor a CMS with the right conductivity, pore size, and stability for your specific application. Whether you need a small batch for lab testing or a bulk order for a full-scale manufacturing system, our team is ready to walk through your needs, share data from our test batches, and work with you to find the perfect CMS solution.
Don’t settle for a generic CMS that checks pore size boxes but fails when it comes to conductivity. Reach out to our team to discuss your requirements, and let’s find the right carbon molecular sieve for your project.
3A Zeolite References
- Bandosz, T. J. (2006). Carbon Materials for Gas Separation and Storage. Elsevier.
- Marsh, H., & Rodriguez-Reinoso, F. (2006). Activated Carbon. Elsevier.
- Maldonado-Hódar, F. J., et al. (2000). Electrical conductivity of carbon molecular sieves prepared from phenolic resins. Carbon, 38(12), 1701-1708.
- Yang, R. T. (2003). Gas Separation by Adsorption Processes. Imperial College Press.
- Lillo-Ródenas, M. A., et al. (2003). Electrical conductivity of activated carbons: Influence of activation and surface chemistry. Carbon, 41(14), 2755-2763.
Henan Sinmat Chemical Co., Ltd.
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E-mail: sales@sinmatzeolite.com
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