{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,8,23]],"date-time":"2026-08-23T05:20:30Z","timestamp":1787462430712,"version":"build-2736575974"},"reference-count":44,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2026,8,21]],"date-time":"2026-08-21T00:00:00Z","timestamp":1787270400000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Nagqu Regional Scientific and Technological Collaborative Innovation Special Project","award":["NQKJ-2025-QY-02"],"award-info":[{"award-number":["NQKJ-2025-QY-02"]}]},{"DOI":"10.13039\/501100012226","name":"Fundamental Research Funds for the Central Universities","doi-asserted-by":"crossref","award":["30925010505"],"award-info":[{"award-number":["30925010505"]}],"id":[{"id":"10.13039\/501100012226","id-type":"DOI","asserted-by":"crossref"}]},{"name":"Key Research and Development Program of Xizang","award":["XZ202501ZY0067"],"award-info":[{"award-number":["XZ202501ZY0067"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Membranes"],"abstract":"<jats:p>Upgrading biogas to pipeline-quality methane requires the efficient removal of CO2, yet conventional physicochemical routes remain energy-intensive. Coupling a CO2-selective membrane with microalgal photosynthetic fixation offers a green alternative, but is constrained by the low CO2\/CH4 selectivity of common membranes and the poor adhesion of microalgae to hydrophobic membrane surfaces. Here, a dual-functional composite membrane was developed that simultaneously provides CO2\/CH4 sieving and a biocompatible interface for microalgal attachment, and was integrated into a microalgae membrane bioreactor (MMBR). A cellulose acetate mixed-matrix membrane incorporating polyethyleneimine-grafted ZIF-8 (CA\/PZIF-8(15)) achieved a mixed-gas CO2 permeability of 122.3 Barrer and a CO2\/CH4 selectivity of 41.17. An ionic-liquid-modified chitosan (CS\/IL) coating, first optimized on a commercial flat-sheet polyethersulfone (PES) membrane used as a model surface for the adhesion study, reversed the surface charge from \u221230.8 to +3.75 mV, lowered the water contact angle to 51.2\u00b0, and increased the day-7 adhesion of Scenedesmus obliquus by ~108%. Transferring the coating onto CA\/PZIF-8(15) further raised the permeability to 138 Barrer and the selectivity to 57.31, placing the composite above the 2008 Robeson upper bound. In the MMBR, CH4 purity reached 95.13% after 48 h; a mass balance on the recirculating gas volume indicated that essentially all of the CO2 removed from the gas phase permeated the membrane, of which an estimated 2% was fixed into microalgal biomass while the remainder was retained in the liquid phase. This work offers a membrane-design strategy that bridges gas-separation functionality and microalgal carbon fixation for sustainable biogas upgrading.<\/jats:p>","DOI":"10.3390\/membranes16080279","type":"journal-article","created":{"date-parts":[[2026,8,21]],"date-time":"2026-08-21T11:37:34Z","timestamp":1787312254000},"page":"279","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":0,"title":["A Dual-Functional CO2-Selective Membrane for Biogas Upgrading in a Microalgae Membrane Bioreactor"],"prefix":"10.3390","volume":"16","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-0927-5727","authenticated-orcid":false,"given":"Yongze","family":"Lu","sequence":"first","affiliation":[{"name":"School of Energy and Environment, Southeast University, Nanjing 210096, China"},{"name":"Key Laboratory of Water Pollution Control and Ecological Restoration of Xizang, National Ethnic Affairs Commission, Xizang Minzu University, Xianyang 712082, China"},{"name":"School of Engineering, Xizang Minzu University, Xianyang 712082, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Xiaohuan","family":"Wang","sequence":"additional","affiliation":[{"name":"Jiangsu Key Laboratory of Chemical Pollution Control and Resources Reuse, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Mingchao","family":"Zhu","sequence":"additional","affiliation":[{"name":"Key Laboratory of Water Pollution Control and Ecological Restoration of Xizang, National Ethnic Affairs Commission, Xizang Minzu University, Xianyang 712082, China"},{"name":"School of Engineering, Xizang Minzu University, Xianyang 712082, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Shouwen","family":"Chen","sequence":"additional","affiliation":[{"name":"Jiangsu Key Laboratory of Chemical Pollution Control and Resources Reuse, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Zhaoxia","family":"Hu","sequence":"additional","affiliation":[{"name":"Jiangsu Key Laboratory of Chemical Pollution Control and Resources Reuse, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Na","family":"Li","sequence":"additional","affiliation":[{"name":"Jiangsu Key Laboratory of Chemical Pollution Control and Resources Reuse, School of Environmental and Biological Engineering, Nanjing University of Science and Technology, Nanjing 210094, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2026,8,21]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"56","DOI":"10.1016\/j.rser.2018.09.003","article-title":"An overview on conversion technologies to produce value added products from CH4 and CO2 as major biogas constituents","volume":"98","author":"Zain","year":"2018","journal-title":"Renew. Sustain. Energy Rev."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"452","DOI":"10.1016\/j.biotechadv.2018.01.011","article-title":"Biogas upgrading and utilization: Current status and perspectives","volume":"36","author":"Angelidaki","year":"2018","journal-title":"Biotechnol. Adv."},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"521","DOI":"10.1016\/j.rser.2015.06.029","article-title":"Selection of appropriate biogas upgrading technology\u2014A review of biogas cleaning, upgrading and utilisation","volume":"51","author":"Sun","year":"2015","journal-title":"Renew. Sustain. Energy Rev."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"727","DOI":"10.1007\/s11157-015-9379-1","article-title":"A review on the state-of-the-art of physical\/chemical and biological technologies for biogas upgrading","volume":"14","author":"Meier","year":"2015","journal-title":"Rev. Environ. Sci. Bio\/Technol."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"641","DOI":"10.1016\/j.renene.2018.06.089","article-title":"Comparison of the biogas upgrading methods as a transportation fuel","volume":"130","author":"Hosseinipour","year":"2019","journal-title":"Renew. Energy"},{"key":"ref_6","doi-asserted-by":"crossref","first-page":"3965","DOI":"10.1016\/j.ijhydene.2022.10.228","article-title":"Biogas upgrading technologies\u2014Recent advances in membrane-based processes","volume":"48","author":"Gkotsis","year":"2023","journal-title":"Int. J. Hydrogen Energy"},{"key":"ref_7","doi-asserted-by":"crossref","first-page":"9393","DOI":"10.1021\/acs.energyfuels.7b00120","article-title":"Upgrading Biogas to Biomethane Using Membrane Separation","volume":"31","year":"2017","journal-title":"Energy Fuels"},{"key":"ref_8","doi-asserted-by":"crossref","first-page":"1649","DOI":"10.1007\/s10311-020-01036-3","article-title":"Membrane-based technologies for biogas upgrading: A review","volume":"18","author":"Reina","year":"2020","journal-title":"Environ. Chem. Lett."},{"key":"ref_9","first-page":"100722","article-title":"Harnessing the potential of microalgae in sequestration of CO2 emissions: Removal mechanisms, optimization strategies, and bioenergy production","volume":"18","author":"Adetunji","year":"2025","journal-title":"J. Hazard. Mater. Adv."},{"key":"ref_10","doi-asserted-by":"crossref","first-page":"102","DOI":"10.1016\/j.biombioe.2014.10.032","article-title":"Photosynthetic CO2 uptake by microalgae: An attractive tool for biogas upgrading","volume":"73","author":"Meier","year":"2015","journal-title":"Biomass Bioenergy"},{"key":"ref_11","doi-asserted-by":"crossref","first-page":"119467","DOI":"10.1016\/j.jece.2025.119467","article-title":"Microalgae fixed flue gas CO2 into biomass: Comparative of life cycle assessment and technical-economic analysis of different technologies","volume":"13","author":"Hu","year":"2025","journal-title":"J. Environ. Chem. Eng."},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"3187","DOI":"10.1016\/j.scitotenv.2018.09.355","article-title":"Microalgal biofilms: A further step over current microalgal cultivation techniques","volume":"651","author":"Mantzorou","year":"2019","journal-title":"Sci. Total Environ."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"331","DOI":"10.1016\/j.rser.2018.04.081","article-title":"Microalgal attachment and attached systems for biomass production and wastewater treatment","volume":"92","author":"Wang","year":"2018","journal-title":"Renew. Sustain. Energy Rev."},{"key":"ref_14","doi-asserted-by":"crossref","first-page":"105941","DOI":"10.1016\/j.biombioe.2020.105941","article-title":"Practical strategies to improve harvestable biomass energy yield in microalgal culture: A review","volume":"145","author":"Hajinajaf","year":"2021","journal-title":"Biomass Bioenergy"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"29","DOI":"10.1016\/j.biombioe.2012.12.019","article-title":"Micro-algae cultivation for biofuels: Cost, energy balance, environmental impacts and future prospects","volume":"53","author":"Slade","year":"2013","journal-title":"Biomass Bioenergy"},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Perez, E.V., Karunaweera, C., Musselman, I.H., Balkus, K.J., and Ferraris, J.P. (2016). Origins and Evolution of Inorganic-Based and MOF-Based Mixed-Matrix Membranes for Gas Separations. Processes, 4.","DOI":"10.3390\/pr4030032"},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"483","DOI":"10.1016\/j.progpolymsci.2007.01.008","article-title":"Mixed matrix membranes (MMMs) comprising organic polymers with dispersed inorganic fillers for gas separation","volume":"32","author":"Chung","year":"2007","journal-title":"Prog. Polym. Sci."},{"key":"ref_18","doi-asserted-by":"crossref","first-page":"17203","DOI":"10.1021\/jacs.8b10138","article-title":"Interfacial Engineering in Metal\u2013Organic Framework-Based Mixed Matrix Membranes Using Covalently Grafted Polyimide Brushes","volume":"140","author":"Wang","year":"2018","journal-title":"J. Am. Chem. Soc."},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"1431","DOI":"10.4028\/www.scientific.net\/AMR.690-693.1431","article-title":"Influence of surface zeta potential on adhesion of Chlorella sp. to substratum surfaces","volume":"690","author":"Zhang","year":"2013","journal-title":"Adv. Mater. Res."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"113514","DOI":"10.1016\/j.colsurfb.2023.113514","article-title":"Microalgae cell adhesions on hydrophobic membrane substrates using quartz crystal microbalance with dissipation","volume":"230","author":"Liao","year":"2023","journal-title":"Colloids Surf. B"},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"101620","DOI":"10.1016\/j.algal.2019.101620","article-title":"Enhancing Scenedesmus obliquus biofilm growth and CO2 fixation in a gas-permeable membrane photobioreactor integrated with additional rough surface","volume":"43","author":"Guo","year":"2019","journal-title":"Algal Res."},{"key":"ref_22","doi-asserted-by":"crossref","first-page":"2071","DOI":"10.1039\/c0cc05002d","article-title":"Rapid synthesis of zeolitic imidazolate framework-8 (ZIF-8) nanocrystals in an aqueous system","volume":"47","author":"Pan","year":"2011","journal-title":"Chem. Commun."},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"3151","DOI":"10.1039\/C7TA10322K","article-title":"In situ synthesis of polymer grafted ZIFs and application in mixed matrix membrane for CO2 separation","volume":"6","author":"Gao","year":"2018","journal-title":"J. Mater. Chem. A"},{"key":"ref_24","doi-asserted-by":"crossref","first-page":"117908","DOI":"10.1016\/j.memsci.2020.117908","article-title":"Sulfonated graphitic carbon nitride nanosheets as proton conductor for constructing long-range ionic channels proton exchange membrane","volume":"601","author":"Lu","year":"2020","journal-title":"J. Membr. Sci."},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Chen, Q., Qi, Y., Jiang, Y., Quan, W., Luo, H., Wu, K., Li, S., and Ouyang, Q. (2022). Progress in Research of Chitosan Chemical Modification Technologies and Their Applications. Mar. Drugs, 20.","DOI":"10.3390\/md20080536"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"3759","DOI":"10.1002\/pat.5792","article-title":"Measuring contact angles on hydrophilic porous scaffolds by implementing a novel raised platform approach: A technical note","volume":"33","author":"Paxton","year":"2022","journal-title":"Polym. Adv. Technol."},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"131","DOI":"10.1016\/j.jconhyd.2015.01.005","article-title":"DLVO and XDLVO calculations for bacteriophage MS2 adhesion to iron oxide particles","volume":"181","author":"Park","year":"2015","journal-title":"J. Contam. Hydrol."},{"key":"ref_28","doi-asserted-by":"crossref","first-page":"1","DOI":"10.1016\/0927-7757(93)80308-2","article-title":"Acid\u2013base interfacial interactions in aqueous media","volume":"78","year":"1993","journal-title":"Colloids Surf. A"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"277","DOI":"10.1016\/j.ces.2018.06.008","article-title":"Improving particle dispersity and CO2 separation performance of amine-functionalized CAU-1 based mixed matrix membranes with polyethyleneimine-grafting modification","volume":"189","author":"Guo","year":"2018","journal-title":"Chem. Eng. Sci."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"390","DOI":"10.1016\/j.memsci.2008.04.030","article-title":"The upper bound revisited","volume":"320","author":"Robeson","year":"2008","journal-title":"J. Membr. Sci."},{"key":"ref_31","doi-asserted-by":"crossref","first-page":"1390","DOI":"10.1126\/science.abl7163","article-title":"Hydrocarbon ladder polymers with ultrahigh permselectivity for membrane gas separations","volume":"375","author":"Lai","year":"2022","journal-title":"Science"},{"key":"ref_32","doi-asserted-by":"crossref","first-page":"235","DOI":"10.1016\/j.memsci.2012.09.006","article-title":"Carbon dioxide selective mixed matrix composite membrane containing ZIF-7 nano-fillers","volume":"425\u2013426","author":"Li","year":"2013","journal-title":"J. Membr. Sci."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"e2848","DOI":"10.1002\/apj.2848","article-title":"Performance of amine-functionalized MIL-53 incorporated thin-film nanocomposite Pebax membranes for CO2\/CH4 mixed gas separation","volume":"18","author":"Fakoori","year":"2023","journal-title":"Asia-Pac. J. Chem. Eng."},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"e52810","DOI":"10.1002\/app.52810","article-title":"UiO-66-NH2 particle size effects on gas separation performance of cellulose acetate composite membranes","volume":"139","author":"Hu","year":"2022","journal-title":"J. Appl. Polym. Sci."},{"key":"ref_35","first-page":"e01758","article-title":"Design of amino acid functionalized ZIF-8\/cellulose acetate mixed matrix membranes for improved gas separation efficiency","volume":"46","author":"Radoor","year":"2025","journal-title":"Sustain. Mater. Technol."},{"key":"ref_36","doi-asserted-by":"crossref","first-page":"118914","DOI":"10.1016\/j.jece.2025.118914","article-title":"Cellulose acetate mixed matrix membranes incorporating APTES-functionalized MOF-5 derived from recycled PET plastic bottles for high-performance gas separation","volume":"13","author":"Radoor","year":"2025","journal-title":"J. Environ. Chem. Eng."},{"key":"ref_37","doi-asserted-by":"crossref","first-page":"3284","DOI":"10.1021\/acs.langmuir.2c00042","article-title":"How Interfacial Properties Affect Adhesion: An Analysis from the Interactions between Microalgal Cells and Solid Substrates","volume":"38","author":"Zeng","year":"2022","journal-title":"Langmuir"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"37","DOI":"10.1016\/j.jbiotec.2022.10.012","article-title":"Marine microalgal biofilm development and its adhesion propensities on commercial membrane via XDLVO approach","volume":"360","author":"Tong","year":"2022","journal-title":"J. Biotechnol."},{"key":"ref_39","doi-asserted-by":"crossref","first-page":"85","DOI":"10.1016\/j.ijggc.2018.07.014","article-title":"Facilitated transport membranes with an amino acid salt for highly efficient CO2 separation","volume":"78","author":"Zhang","year":"2018","journal-title":"Int. J. Greenh. Gas. Control"},{"key":"ref_40","doi-asserted-by":"crossref","first-page":"118812","DOI":"10.1016\/j.seppur.2021.118812","article-title":"Gas separation performance of carbon dioxide-selective poly(vinyl alcohol)\u2013ionic liquid blend membranes: The effect of temperature, feed pressure and humidity","volume":"270","author":"Jansen","year":"2021","journal-title":"Sep. Purif. Technol."},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"307","DOI":"10.1016\/j.biortech.2012.03.074","article-title":"Growth characteristics of Chlorella sorokiniana in airlift and bubble column photobioreactors","volume":"116","author":"Kumar","year":"2012","journal-title":"Bioresour. Technol."},{"key":"ref_42","doi-asserted-by":"crossref","first-page":"120101","DOI":"10.1016\/j.watres.2023.120101","article-title":"Effect of EPS production on the performance of membrane-based biofilm reactors","volume":"240","author":"Kim","year":"2023","journal-title":"Water Res."},{"key":"ref_43","doi-asserted-by":"crossref","first-page":"111661","DOI":"10.1016\/j.rser.2021.111661","article-title":"Biological characteristics of energy conversion in carbon fixation by microalgae","volume":"152","author":"Zeng","year":"2021","journal-title":"Renew. Sustain. Energy Rev."},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"111343","DOI":"10.1016\/j.rser.2021.111343","article-title":"Current status of biogas upgrading for direct biomethane use: A review","volume":"149","author":"Khan","year":"2021","journal-title":"Renew. Sustain. Energy Rev."}],"container-title":["Membranes"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/2077-0375\/16\/8\/279\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2026,8,23]],"date-time":"2026-08-23T04:26:38Z","timestamp":1787459198000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/2077-0375\/16\/8\/279"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2026,8,21]]},"references-count":44,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2026,8]]}},"alternative-id":["membranes16080279"],"URL":"https:\/\/doi.org\/10.3390\/membranes16080279","relation":{},"ISSN":["2077-0375"],"issn-type":[{"value":"2077-0375","type":"electronic"}],"subject":[],"published":{"date-parts":[[2026,8,21]]}}}