import React from 'react';
import Button from '@material-ui/core/Button';
export default function DisableElevation() {
return (
<Button variant="contained" color="primary" disableElevation >
Disable elevation
</Button>
);
}

import React from 'react';
import Button from '@material-ui/core/Button';
export default function DisableElevation() {
return (
<Button variant="contained" color="primary" disableElevation >
Disable elevation
</Button>
);
}

It is quite simple just make border:none and outline:none that's it for a corresponding component.
style={{
border:"none",
outline:"none"
}}
The problem was using both MUI and bootstrap. remove importing 'bootstrap/dist/css/bootstrap.min.css' in project and after remove bootstrap, problem will solve
you don't need this both libraries for ui dev works you can do most of things by using one. You can use either MUI or bootstrap as your wish but using both in same project cause to UI effects