The last decade has seen the ascendence of technologies based on micro- and nanobubbles for a wide range of applications, including, but not limited to, lake cleaning, aquaculture, and biomedicine. The bubble suspensions that mediate such technologies are often produced using methods that incur large amounts of energy as well as costs, such as through vigorous mechanical aeration and ultrasound. Here, we present a method to passively produce bubble suspensions with tuneable composition using microporous materials such as carbon and zeolite molecular sieves, leveraging on the high adsorption energy of such materials to create suspensions rich in dissolved gas. Apart from being energy efficient, this method distinguishes itself from commercial methods of producing bubble suspensions through its ability to control gas composition: carbon molecular sieves produce a suspension that is sparged of oxygen but nitrogen-rich, whereas zeolite molecular sieves produce the converse outcome. Our findings not only reduce barriers towards the commercialisation of technologies dependent on bubble suspensions but also invite significant new applications for bubble technologies in areas such as aquaculture or medicine, where there is still an unfulfilled demand to tune the chemical environment of bubble suspensions.