Is there a bijective, monotonically increasing, strictly concave function from the reals, to the reals?

$$ f(x) = x-e^{-x} $$ is such a function. Since $f''(x) = -e^{-x}$ is always negative, it is strictly concave, and it's not hard to show it hits every real.

Even better, $$ f(x) = 2x -\sqrt{1+3x^2} $$ has $f''(x) = -3(1+3x^2)^{-3/2} < 0$ everywhere and the explicit inverse $f^{-1}(x) = 2x+\sqrt{1+3x^2}$, clearly defined for all $x$.

EDIT: Since it was requested in the comments, here is a plot of this function and its inverse: Plot

Note that even though the growth rate for positive $x$ is slow, the function is asymptotically linear (with slope $2-\sqrt{3}\approx 0.268$) and thus unbounded.


How about

$f(x)=\left\{\begin{array}{cc} \ln(x+1)& &x\ge 0\\1-e^{-x}& &x<0\end{array}\right.$


$f(x) = \pi x+ \int_0^x \arctan (-t)\,dt$ is an example. Many more examples like this one can be constructed.