'm just guessing this was the subject of your reading. They still produce CO2, but I guess you could pair one of these with a liquid metal alloy electrolysis unit to convert the CO2 into solid carbon, which you could burn to run the turbine to generate electricity to run the electrolysis unit. Rinse repeat!
The Big Tat is on the hunt but has scented false spoor!
'Tis not reading I am doing but writing. The subject of the Small Business Innovation Research grant proposal is, indeed, a ceramic heat exchanger for the type of turbine generator that surfaced in your literature search. However, our innovation focuses on the high temperature burning of syngas (smoke), a co-product generated during the pyrolysis of woody biomass - the other product being biochar. There is also a 3rd co-product of heat that is not used up in making electricity that can be used for building or industrial process heat.
Because the biochar is a form of carbon, graphene, that is chemically and physically recalcitrant to change, it may be used in the soil and in other durable products as a carbon sequestration substance. And because it came from plants, which took it from the atmosphere, it represents a bona fide CO2 drawdown opportunity. Thus and thereby, it is the only carbon negative energy source in existence!
But the alchemy explanation is easier for most folks to grok...
You never change things by fighting the existing reality. To change something, build a new model that makes the old model obsolete. R. Buckminster Fuller