Heat Of Sorption Research Articles

Heat transfer constraints and performance mapping of a closed liquid sorption heat storage process

Sorption storage is a potential game changer for heat storage in buildings, providing high volumetric energy storage density and no loss over storage time. Application specific temperatures and material specific thermodynamic properties are recognized as key for potential performance evaluation. Nevertheless, in system operation, finite heat and mass transfer kinetics detract from the theoretical maximum performance. In this study, it is found that a nonlinear relationship between temperature gain and heat release of the sorbent, afflicts an unavoidable restriction to the performance potential. Heat transport increases as temperature gain decreases, bringing about a temperature induced heat transfer stagnation to a heat transport fluid with linear temperature to heat gain correlation.In this paper, we present the background for performance analysis with emphasis on this nonlinear relationship. We propose a method for performance mapping, including the sorbent equilibrium line (the state where the sorbent is in temperature, concentration and vapor pressure equilibrium) and the unavoidable deviation from this line due to the afore stated non-linearity. As an example of this proposed mapping, we visualize results from an absorption process with liquid aqueous sodium hydroxide and water.Due to the nonlinear temperature rise in heat release, we conclude that it is important to operate a sorption heat storage system in a way that only the minimum required temperature rise is achieved. By doing so, the heat transport fluid capacity is increased in respect to the sorbent capacity, augmenting heat transfer and improving the energy density.

Estimation of Thermodynamic Parameters for Better Conservation of Fresh Tomato (<i>Lycopersicum esculentum</i>)

Knowledge of the state of water balance of agro-food products is an essential step in drying or storage operations for preservation. Our study made it possible to determine the thermodynamic parameters which influence the storage conditions of fresh tomatoes grown in the south of Benin; and to predict its hygroscopic behavior during post-harvest storage. The desorption isotherms obtained at 40℃, 50℃ and 60℃, by the static gravimetric method using saturated saline solutions, are compared with those of the theoretical models of Brunauer, Emmet and Teller (BET), SMITH, PELEG and Guggenheim-Anderson-Boer (GAB). An adjustment of the experimental points, on the theoretical models, was made thanks to the numerical method which exploits the fminsearch algorithm under the MATLAB software, version R2018a. The GAB model at 50℃ faithfully reproduces the experimental desorption curves for water activities from 5.5% to 82.3%. The net isosteric heat of sorption was determined using the Clausius-Clapeyron equation, it increases when the degree of dehydration of the product increases. The applied isokinetic theory and enthalpy-entropy compensation are consistent.

Experimental investigation on a strontium chloride/ammonia sorption heat storage system

• A thermochemical sorption heat storage system has been established. • The total highest heat storage density is 1871.03 kJ/kg SrCl 2 composite sorbent. • The total highest heat storage efficiency of the sorption system is 92.74%. Thermochemical sorption heat storage based on solid-gas interaction is considered as a cutting-edge technology for harvesting solar energy and industrial waste heat due to the significant advantages of high heat storage density, flexible working modes and long-term storage capacity with negligible heat loss. As a vital technology to enhance energy infrastructures, the thermochemical sorption heat storage has aroused extensive interest in the past decade. In this work, a solid-gas thermochemical sorption system was established and investigated for recovering the thermal energy. Working pair of strontium chloride/ammonia was selected, and strontium chloride composite sorbents were synthesized using the expanded graphite as matrix. The heat storage performances of strontium chloride/ammonia sorption system at the different temperatures were experimentally investigated. Under the condition of 92 °C charging temperature, 40 °C discharging temperature and -5 ℃ condensation/evaporation temperature, the highest sorption heat storage density of the sorption system obtained is up to 1630.78 kJ/kg SrCl 2 (or 1386.16 kJ/kg composite sorbent), and the total heat storage density can reach 2201.21 kJ/kg SrCl 2 (or 1871.03 kJ/kg composite sorbent). The total energy efficiency of the sorption system increases from 74.71% to 92.74% with the heat storage temperature rising from 68 ℃ to 92 ℃. Results indicated that strontium chloride and its composites are promising heat storage materials, and revealed great potentials of thermochemical sorption heat storage technology for rational and efficient utilization of thermal energy.

Zeolite 13X/MgSO4 as a potential heat storage material: thermal performance characterization and sorption kinetics enhancement

Solid–gas thermochemical sorption heat storage is an efficient heat storage technology.

Constructal design of weight optimized metal hydride storage device embedded with ribbed honeycomb

Solid state storage of hydrogen offers few advantages over compressed and liquefied forms. As heat transfer being the major factor controlling charging and discharging, several thermal enhancement methods were reported in literature. However parasitic weight of thermal enhancement structures embedded to the storage bed can reduce its gravimetric storage capacity. As total weight of the device for given hydrogenation capacity and charging rate being an important factor, these structures needs to be weight optimized. The present study propose a ribbed honeycomb embedded to the multi-tubular storage device with sodium alanate as the storage alloy. The shape and size of this conform to the constructal law, analogous to bio transport systems. This ensures efficient transfer of sorption heat from the point of maximum temperature in the hydride bed to the coolant. The device designed for charging 0.01 kg of hydrogen in 10 min weighs 1.2 kg at optimum length/thickness ratio. This numerical study is conducted using COMSOL Multiphysics™ commercial code.

Thermochemical sorption heat storage: Investigate the heat released from activated carbon beads used as porous host matrix for MgSO4 salt

For sustainable and cost-effective thermal management and energy storage, sorption-base thermal storage has received a lot of attention. However, the low sorption capacity of sorbents has long been a barrier to high energy-density sorption-based thermal storage. We present a new promising composite with high heat release and sorption capacity. The use of MgSO4/bead activated carbon composites in thermochemical sorption heat storage has been investigated. Because of the highly developed microporosity and high apparent specific surface area of about 1300 m2/g, bead activated carbon (BAC) is a potential candidate as support for salt/support composites for thermochemical heat storage. Also, the thermal conductivity of BAC has been measured and found to be 0.14 W/mK, which is higher than that of other materials like zeolites or alumina. This high thermal conductivity can influence the water sorption equilibrium, controlling the temperature of the solid, avoiding hot-spots, and thus preventing desorption during the hydration step. In stationary conditions (RH = 60 %, gas flow = 30 mL/min), the water sorption capacity of BAC was 0.138 g/g. This value was 2.32 times higher when the salt was dispersed into the BAC matrix, for the composite 7.6-MgSO4/BAC. A water adsorption capacity, higher than the theoretical value, was observed and attributed to the condensation of water molecules within the porous structure, resulting in a high thermal energy density. The 7.6-MgSO4/BAC composite achieved the highest heat of hydration of 920 J/g. The 10 hydration/dehydration cycles performed (dehydration at 150 °C and hydration at 30 °C with a RH of 60 %) confirmed the composite's excellent stability. This research provides a promising low-carbon pathway for the efficient capture, storage, and utilization of thermal energy.

Static Water Vapor Sorption Properties of Honey

Abstract Static sorption properties of pine honey (PH) and citrus honey (CH) were studied at 20, 30 and 40°C. Yeast formation was observed on the surface of honeys at water activity (aw)>0.7 at all temperatures. Visible yeast formation (YF) took place earlier in PH than in CH under the same conditions due to its characteristic higher pH and lower monosacchride content. The temperature was insignificantly effective on YF (p>0.05). The honeys exhibited a sorption isotherm (SI) in the shape of a “J”. Their SIs exhibited desorption and adsorption at aw<0.7 and aw>0.7, respectively and the desorption part was almost linear. Aw=0.7 emerged as a border between the absence and presence of YF and between the desorption and adsorption. The SIs of honeys were insignificantly affected by temperature (p>0.05). PH had a significantly lower SI than that of CH (p≤0.05) due to its characteristic lower monosacchride content. GAB equation exhibited a good fit to the honeys' SIs. Sorption heat vs equilibrium moisture content (EMC) revealed monolayer, multilayer and loosely bound free water regions in the SIs of PH and CH.

Experimental study on the sorption performance of New–Fashioned silver getters compared with the traditional PdO in High–Vacuum multi–layer insulation vessels

Hydrogen (H2) getter is one of the indispensable tools in high–vacuum multi–layer insulation (HVMLI) vessels. This study investigated several new–fashioned and low–cost H2 (i.e. silver getters) getters to replace expensive palladium oxide (PdO). The silver getters (SPSG, BPSG and Ag400B2) combined the advantages of chemical and physical sorption, which is referred to as physicochemical sorption in this study. An experimental platform was set up to test the properties of the silver getters. The sorption capacity of the silver getters was calculated using the constant volume method. The results reveal that BPSG, SPSG29g, SPSG51g and Ag400B2 have sorption capacities of 6.23%, 0.094%, 0.097% and 14.54% of that of PdO, respectively. However, the manufactured cost of physical chemisorption getters is just 0.4%–3% of that of PdO. Furthermore, when PdO sorbs H2, a substantial amount of sorption heat is generated, posing a potential threat to HVMLI vessels. Therefore, it is recommended to use 7 times Ag400B2 and 16 times BPSG instead of palladium oxide as the cryogenic getters under equivalent conditions. These findings provide a basis for applying silver getters in the HVMLI vessels, which greatly reduce the cost of cryogenic getters.

Novel Polyelectrolyte Complex Membranes Containing Carboxymethyl Cellulose–Gelatin for Pervaporation Dehydration of Azeotropic Bioethanol for Biofuel

Polyelectrolyte complex membranes (PECMs) were prepared by combining sodium carboxymethyl cellulose (NaCMC) and gelatin (Ge) with variations in the Ge content in the NaCMC matrix. Characterization methods, such as infrared spectroscopy (FTIR), wide-angle X-ray diffraction (WAXD), thermogravimetric analysis (TGA), scanning electron microscopy (SEM), contact angle analysis (CA), and universal testing machines (UTM) were used to investigate the physicochemical studies of the prepared membranes. The pervaporation characteristics of membranes with Ge content were investigated using an azeotropic mixture of water and bioethanol. The obtained data revealed that the membrane with 15 mass% of Ge (M-3) showed a maximum flux of 7.8403 × 10-2 kg/m2·h with separation selectivity of 2917 at 30 °C. In particular, the total and water flux of PECMs are shown as very close to each other indicating that the fabricated membranes could be employed to successfully break the azeotropic point of water-bioethanol mixtures. Using temperature-dependent permeation and diffusion data, the Arrhenius activation parameters were calculated, and the obtained values of water permeation (Epw) were considerably smaller than bioethanol permeation (EpE). Developed membranes showed the positive heat of sorption (ΔHs), suggesting that Henry's sorption mode is predominant.

Discharging performance prediction of experimentally tested sorption heat storage materials with machine learning method

In this study, the usability of the machine learning method in predicting the discharge performance of experimentally tested sorption heat storage materials was investigated. Experimental data was obtained from a lab scale fixed-bed thermochemical heat storage unit. 9 candidate composites were tested under different inlet conditions. Based on the experimental data, moisture sorption rates, heat output, exergy output and energy storage densities were determined. For the 6 cycles testing, highest average heat and exergy output were obtained with vermiculite/LiCl composite with the values of 0.83 kW and 0.013 kW, respectively. On the other hand, P-CaCl2 was found as the most durable material in terms of energy storage density (296 → 209 kWh/m3). A multilayer perceptron artificial neural network was established to evaluate measured data and its prediction performance was extensively studied. In the model 54 experimental data sets were utilized, consisting of 6 cycles testing of 9 different composite sorbents. Levenberg-Marquardt algorithm was benefited as the training one in the artificial neural network model established and the Tan-Sig and Purelin functions were selected as the transfer one in the multilayer neural network with 7 neurons in the hidden layer. According to the mathematical definition of the discussed statistical metrics, experimental data were used to compare them to the predicted output in order to verify the reliability of the proposed ANN model; and the analysis of the model was performed by examining the coefficient of determination, mean squared error, and deviation values, which were assumed as performance parameters, in detail. The deviation rate between the prediction values acquired from the artificial neural network and the practical data was determined as less than ±5 %. The acquired findings showed that artificial neural networks, which is one of the common machine learning algorithms, is a preferable method that can be employed to estimate the discharge performance of sorption heat storage materials.

Molecular Simulation of Diffusion and Competitive Sorption of CH4 and CO2 in Shale Nanopores

Based on the competitive adsorption of CH4 and CO2, molecular dynamics (MD) and Grand Canonical Monte Carlo (GCMC) are used to study the mechanism of increasing shale gas recovery by carbon dioxide injection. The influence of different factors on the diffusion capacity of CH4 in unrestricted space and restricted space is analyzed, and the diffusion capacities of CH4 and CO2 in shale nanopores are compared. Under different conditions, the difference in the sorption amount and sorption heat of CH4 and CO2 is studied, and the displacement simulation of CH4 and CO2 is conducted. The obtained results show that the diffusion capacity of CH4 in restricted space is much smaller than that in unrestricted space, and the difference between them is related to temperature, pressure, and pore size. When pressure exceeds 10 MPa, the difference gradually decreases. The diffusion capacity of CO2 is weaker than that of CH4 under the same conditions, which contributes to the retention of CO2. There is a competitive sorption relationship between CH4 and CO2. The sorption amount and sorption heat of CH4 and CO2 are affected by the combination of pressure, temperature, density ratio, pore size, and mineral type. The adsorption capacity of CO2 is much higher than that of CH4. When sorption conditions are more favorable, the adsorption difference between CH4 and CO2 will become larger. In shale nanopores, CO2 can replace CH4 that is adsorbed on the pore surface to improve shale gas recovery.

High hexane sorption capacity of loosely crosslinked PDMS rubbers at low temperatures: Macromolecular and physicochemical elucidation for VOC recovery

A series of soft polydimethylsiloxane (PDMS) rubbers was obtained by diluting reaction mixtures of a PDMS macromer and a crosslinker with an organic solvent. The degree of swelling of the softest rubber was 600 wt% when immersed in pure hexane at room temperature. From the Flory–Huggins equations, the free energy change for hexane sorption per 1 g rubber was calculated to be −7.4 J g−1 and the entropy contribution of the polymer chains was 1.6 J g−1 larger than that of the conventional PDMS rubber. The loosely crosslinked PDMS rubber could sorb 776 mg g−1 of hexane at 298 K and 606 mg g−1 at 195 K. The latter value was 4.4 times larger than that of the conventional PDMS rubber. At a low pressure of 23 Pa, the PDMS rubber sorbed a 3500-fold greater amount of hexane at 195 K, as compared with the value at 298 K. This high sorption amount is because the expansion energy of such soft PDMS rubber is small. The sorption heat of the loosely crosslinked PDMS rubber was 30.3 kJ mol−1 when calculated from the Clausius–Clapeyron equation. This value is substantially smaller than that of commercial activated carbon (75 kJ mol−1). Unlike activated carbon, PDMS rubber is insensitive to water and selectively sorbs VOCs even under a saturated humidity. Because of the large swelling potential and small sorption/desorption heat, the loosely crosslinked PDMS rubber will be an indispensable sorbent for the recovery of flammable gasses such as alkane and iso-alkane VOCs in the chemical and oil and gas industries.

High efficient pre-combustion CO2 capture by using porous slurry formed with ZIF-8 and isoparaffin C16

Integrated gasification combined cycle (IGCC) power generation has drawn more and more attention because of the increasing demand for zero CO2 emission. H2/CO2 mixture with middle/higher pressure like IGCC gas is usually separated by using low energy consumption physical absorption approach. Here, for upgrading traditional physical absorbents, we report a new porous slurry formed with ZIF-8 and isoparaffin C16 to raise CO2 capture capacity and selectivity. The properties and sorption behaviors of this slurry have been experimentally investigated, and the content of ZIF-8 is optimized as 20 wt%. The optimized slurry exhibits low viscosity (11.02–2.75 mPa·s when temperature ranges from 273.15 to 303.15 K), sufficiently high sorption speed, low CO2 sorption heat (9.39–18.47 kJ/mol, decreasing with increasing CO2 loading). More importantly, the slurry exhibits much higher CO2 sorption capacity (e.g., 3.39 mol/L/MPa at 0.1 MPa and 273.15 K, vs. 2.48 mol/L/MPa for dimethyl ethers of polyethylene glycol (DEPG) and 2.22 mol/L/MPa for propylene carbonate (PC)) and selectivity over H2 (17.4–205, which could be one time higher than DEPG and three times higher than PC). The recyclability of this slurry system is also excellent. The 98% sorption capacity is recovered by vacuuming for 5 min without heating, showing that the easy sorption-desorption cycle can be completed only via pressure swing. We believe ZIF-8/isoparaffin C16 slurry would be a promising alternative to existing commercial CO2 absorbent for separating IGCC gas with higher efficiency and lower energy cost.

Moisture Sorption Isotherms of Sweet Cherry (Prunus Avium L.): Comparative Study of Kinetics and Thermodynamic Modeling of Five Varieties

Moisture sorption isotherms of five sweet cherry cultivars (Prunus avium L.) at three temperatures of 30°C, 40°C, and 50°C, and water activity range of 0.057-0.898 were determined using the static gravimetric method. The sorption isotherms of all cultivars decreased with increasing temperature, and they all exhibited type II behavior according to the classification of IUPAC (International Union of Pure and Applied Chemistry). The isosteric heat of sorption, differential entropy, spreading pressure, and water surface area were determined, and the energy associated with the sorption processes was defined. The curves were fitted to GAB, PELEG, and ENDERBY models, and the GAB model gave the best fit for the whole set of data. The enthalpy-entropy compensation proved that the process occurs spontaneously and is fully controlled the enthalpy. The spreading pressure value varied with temperature in all sweet cherry cultivars in both the desorption and adsorption processes. The average surface area varied from 78.05 to 214.02 m2/g for desorption and from 49.0 to 204.4 m2/g for adsorption from 30 to 50°C.

Water sorption behaviour of commercial furcellaran

Water sorption isotherms are important tool for designing the technological processes and predicting stability and shelf life of food. The aim of the work was to determine the water sorption isotherms of commercial furcellaran at different temperatures (20, 35 and 50 °C) using a gravimetric method under different levels of relative humidity (19–95%). The experimental data obtained have been interpreted in the terms of various isotherm models and it was found that the best results were obtained with the Peleg model (P < 2.1%; RSME <0.01; R2 = 1.00). The obtained isotherms followed the type II pattern and, in all cases, the sorption capacity increased with increasing water activity and decreased with increasing temperature. The maximum net isosteric heat for adsorption and desorption was 938.9 and 988.6 J g −1, respectively, at an equilibrium moisture content of 0.05 gw gdb−1. The net isosteric heat of sorption decreased exponentially with increasing moisture content and approached zero at 0.26 gw gdb−1 for adsorption and 0.32 gw gdb−1 for desorption. The developed mathematical relationships can be used to optimize the drying processes and storage conditions of furcellaran.

Desorption and thermophysical properties of feijoa pulp as affected by temperature and moisture content

ABSTRACT Feijoa has a high nutraceutical and agro-industrial potential, an attractive opportunity for Colombia to enter new markets with innovative products. However, there is little knowledge about its behavior and requirements for its proper industrial processing. The studies of thermophysical and sorption properties are fundamental for analyzing and optimizing the different unit operations, evaluation, and product quality control. This study aimed to determine and mathematically model the physical, thermal, and water desorption properties of feijoa pulp in the physiological ripening stage. The desorption isotherms were determined using the gravimetric method, based on saturated salts’ solutions to create atmospheres of controlled relative humidity (RH, %), in this case, at temperatures (T) of 8°C, 23°C, and 38°C and water activities (aw) between 0.07 and 0.98. From the isotherms model that best fits the experimental data, the isosteric heat of sorption (Qs ), differential entropy (ΔSdiff ), and Gibbs free energy (ΔG) were calculated. The density (ρ), thermal conductivity (k), and specific heat capacity (cp) properties were determined and modeled at different moisture contents (H: 75%, 80%, 85%, and 90%) in the temperature range (T) 20 to 80°C, using the pycnometer method, concentric cylinder method, and differential scanning spectrophotometry (DSC), respectively. The desorption isotherms of the feijoa pulp were type III with equilibrium moisture contents (Xe ) between 0.1246 and 5.5135 kg/kg (dry basis, d.b.), a monolayer moisture content of 0.2 kg/kg (d.b.); and spontaneity of the sorption phenomenon. Both cp and k depended more on H than on T; while ρ showed an equal relationship with both factors; these behaviors are characteristic of high humidity foods. The mathematical models obtained in this study are a valuable contribution for the food industry for an effective agro-industrialization, use, and added value of feijoa pulp through the design, control, and optimization of processes and equipment that involve the transfer of heat and matter.

Study on equilibrium moisture sorption characteristics and modeling of Karaya (Sterculia urens Roxb.) gum

BackgroundKaraya gum is heavily acetylated polysaccharide and used for medicinal purposes as a bulk-forming laxative. It is also used in the paper and textile industries as well as food stabilizer. So its moisture sorption behavior study is important. The moisture sorption isotherms of karaya gum were investigated at four experimental temperatures (30, 40, 50 and 60 °C) under the water activities range from 0.10 to 0.95 using static gravimetric method.ResultsMaximum value of equilibrium moisture content (EMC) of karaya gum (39.7%, db) was noted with the set of highest water activity (0.92) at lowest temperature (30 °C) and minimum value of EMC (2.5%, db) with lowest water activity (0.11) at highest temperature (60 °C). The sorption data were fitted with GAB, Iglesias and Chirife, Caurie, Halsey and BET models. The adequacy of the sorption isotherm models were observed statistically using goodness of fit parameters. The well-known GAB model best interpreted the equilibrium data in a satisfactory manner in the test gum. The monolayer moisture content, estimated using GAB model, was found to be 12.66 g/100 g and 7.4 g/100 g gum at 30 °C and 60 °C, respectively. The isosteric heat of sorption was found to be maximum (36.24 kJ/mol) at 5% moisture content (db) of karaya gum.ConclusionMoisture sorption behavior of karaya gum was found to be temperature dependent. EMC decreases with the increase in temperature at particular water activity. The sorption behavior of the test gum expressed the typical type-II sigmoid-shaped curve. Isosteric heat of sorption of karaya gum was decreased with the increase in moisture content.

On the rate of cooling of aerated food grains

Aeration is one of the most powerful tools available to the managers and handlers of stored grains. Irrespective of the initial temperature and moisture content of the grains, the biological and chemical phenomena that occur in the stored grains are significantly influenced by the wet bulb temperature of the air entering the grain. Several authors have developed mathematical expressions to estimate the rate at which aerated stored grains and other hygroscopic materials cool. They refer to ‘difficulties in comprehension’, remark that ‘results are difficult to interpret’ and ‘necessarily complicated’. The principal objective of this work is to clarify and quantify the factors that determine the rate of cooling aerated food grains. This is achieved by deriving an equation that arises as a direct consequence of the conservation of energy and moisture in aerated grains. It is found that the rate of cooling of aerated grains depends strongly on the sorption isotherm, a mathematical function that relates grain moisture content to the equilibrium relative humidity and temperature of their surrounding atmosphere. The integral heat of wetting, a function of the sorption isotherm, contributes to the effective specific heat of grains. However, its effects are typically neglected in analyses of the rate at which aerated grain cools because published sorption isotherms are insufficiently accurate for them to be included. It is proposed that a multidisciplinary approach be taken to measuring the psychrometric properties of food grains. • A new and simple equation is derived for the rate of cooling of aerated grains. • The equation highlights the factors that govern the rate of grain cooling. • Published sorption data lead to inconsistent values of the heat of sorption.

Investigación de la cinética de secado y las condiciones de secado sobre parámetros bioquímicos, sensoriales y microestructurales de arilos de granada “Sefri” (Punica granatum L. una variedad marroquí)

The study evaluated the application of four drying temperatures inside a newly developed hybrid indirect solar dryer in forced convection (at 40, 50, 60, and 70°C) compared to a direct solar dryer (Greenhouse) for the processing of the Moroccan Sefri pomegranate arils. The thermodynamical analysis allows characterizing the physical properties of the arils using some parameters such as optimal water activity, net isosteric heat of sorption, and effective moisture diffusivity. The biochemical analysis studied included total proteins, sugars, vitamin C, and total anthocyanins, hygrometric properties, microstructure modification, and sensory evaluation. Generally, drying led to a reduction in all parameters. However, lower drying temperature processes (indirect convective solar drying at 40°C and 50°C) give the best results for pomegranate arils. Greenhouse dried samples had almost the lower quality in all parameters. The color is more preserved at indirect convective solar drying at 40°C. However, indirect convective solar drying at 50°C was most appreciated by consumers with higher scores on the sensory evaluation test. As the first study of the thermodynamic and biochemical investigation of dried pomegranate arils in Morocco, this work intended to be the first step in developing controlled new high-quality products for the Moroccan market.

Significantly enhanced gas separation properties of microporous membranes by precisely tailoring their ultra-microporosity through bromination/debromination

Tailoring the ultra-microporosity of polymer and carbon molecular sieve membranes (CMSM) is vital to their gas separation properties. Herein, we adopted a simple novel bromination/debromination method to tune the ultra-microporosity and gas separation properties of a triptycene-based polyimide of intrinsic microporosity (PIM-PI) and its derived CMSM. The brominated PIM-PI showed higher free volume, larger surface area, and ∼ 8 times gas permeability without scarifying selectivity. This is due to the bromine introduction in the main chain induced huge increased ultra-microporosity that caused strong molecular sieving effect. After debromination at 550 °C, the CMSM from the brominated PIM-PI displayed larger pore volume, narrower pore size, ∼ 9-fold enhanced gas permeability and same selectivity than the non-brominated counterpart. The corresponding DBPI-550 demonstrated an unprecedented CO2 permeability of 20639 Barrer combined with CO2/N2 and CO2/CH4 selectivity of 29.2 and 30.9, respectively. Thermal dynamic results showed that this main chain bromination enhanced separation property by improving the activation energy of diffusion (Ed). The diffusion transition state theory suggested this is contributed by the energetic factor of selectivity (Eenthalpic). The debromination improved activation energy of permeation originated from its decreased heat of sorption (ΔHs). This bromination/debromination technique provided a facile method to editing the ultra-microporosity of the resulting membranes, and shed light on the future designing of high performance industrial gas separation membranes.