Quantum Schur duality of affine type C with three parameters

We establish a three-parameter Schur duality between the affine Hecke algebra of type C and a coideal subalgebra of quantum affine $\mathfrak{sl}_n$. At the equal parameter specializations, we obtain Schur dualities of types BCD.
25 pages. Minor corrections, to appear in Math. Res. Letters